In a table, when I try assigning a value to a new column based on some criteria, I get error that "assignment to elements using simple assignment statement is not supported"

I have a table for which I create an index where the values in a particular column are not NaN. I then try to use this index to create an entry into a new array and replace the values at the corresponding index (preloaded with '0000') with '0001'. I will then add this array to the table as a new column.

My intention is to fill the corresponding indx in the column with '0001', if the value in the newTable.PEM1_GA_Current_Estimate_Error a valid number (not NaN).

PEM1b ='0001';
PEM2b ='0010';
PEM3b = '0100';
PEM4 = '1000';

temp={};
indx=(find(newTable.PEM1_GA_Current_Estimate_Error ~= NaN))
temp ={repmat('0000',size(newTable,1),1)}
temp{indx} = PEM1b

%...and add this array as a new column to the table

the last assigment in the code above generates this error:

Assigning to 2609 elements using a simple assignment statement is not supported. Consider using comma-separated list assignment.

I don't think I should need a for loop to iterate through each row and replace the value at the "indx" location --what am I doing wrong?

I included the data....thank you.

[Voss]

Don't use == or ~= to compare to NaN, because NaN is not equal to NaN.

Consider this vector x:

x = [1 NaN 3 NaN 5];

Checking that each element of x is not equal to (~=) NaN indicates that all elements of x are non-NaN, which is obviously not the case.

x ~= NaN

ans = 1x5 logical array
   1   1   1   1   1

That happens because NaNs are considered not equal to each other (so NaN ~= NaN is true):

NaN ~= NaN

ans = logical
   1

Instead, use the isnan() function to determine whether each element of an array is NaN, as in:

~isnan(x)

ans = 1x5 logical array
   1   0   1   0   1

[Voss]

newTable = load('data.mat').newTable

newTable = 2609x17 table
    LPE_VBAT    PEM1_LPE_ZM    PEM1_LPE_EXP_GA_CURR    PEM1_INVERTER_CURRENT    PEM1_GA_Current_Estimate_Error    PEM2_LPE_ZM    PEM2_LPE_EXP_GA_CURR    PEM2_INVERTER_CURRENT    PEM2_GA_Current_Estimate_Error    PEM3_LPE_ZM    PEM3_LPE_EXP_GA_CURR    PEM3_INVERTER_CURRENT    PEM3_GA_Current_Estimate_Error    PEM4_LPE_ZM    PEM4_LPE_EXP_GA_CURR    PEM4_INVERTER_CURRENT    PEM4_GA_Current_Estimate_Error
    ________    ___________    ____________________    _____________________    ______________________________    ___________    ____________________    _____________________    ______________________________    ___________    ____________________    _____________________    ______________________________    ___________    ____________________    _____________________    ______________________________

        0             0                   0                    -1.43                           NaN                      0                   0                     9.73                           NaN                     0                  0                      -0.478                        NaN                     5.41                 129                      109                         NaN              
      530          4.21                 126                     2.62                           NaN                   4.65                 114                     46.7                        2.4411                     0                  0                      -0.356                        NaN                     5.06                 105                     1.97                         NaN              
      530          4.21                 126                     66.3                        1.9005                      0                   0                   -0.343                           NaN                     0                  0                      -0.546                        NaN                     5.06                 105                     57.7                         NaN              
      531          4.91                 108                     97.4                        1.1088                   4.49                 118                      109                        1.0826                     0                  0                        -1.1                        NaN                     4.19                 127                      110                         NaN              
      590          4.62                 128                    -1.27                           NaN                    5.3                 111                     65.3                        1.6998                     0                  0                      -0.515                        NaN                     5.26                 112                     35.8                         NaN              
      535          5.76                  93                     39.7                        2.3426                    5.3                 101                     66.9                        1.5097                     0                  0                      -0.171                        NaN                     5.06                 106                     3.26                         NaN              
      535          5.76                  93                     82.1                        1.1328                    5.3                 101                       91                        1.1099                     0                  0                      -0.222                        NaN                        0                   0                    0.454                         NaN              
      524          5.93                88.4                     76.3                        1.1586                   6.45                81.2                     73.7                        1.1018                     0                  0                      -0.761                        NaN                     6.25                  84                     69.8                         NaN              
      589          5.33                 110                     3.21                           NaN                      0                   0                   0.0767                           NaN                     0                  0                      -0.152                        NaN                     4.99                 118                     36.7                         NaN              
        0             0                   0                    -1.37                           NaN                      0                   0                     5.44                           NaN                     0                  0                     -0.0206                        NaN                        5                 138                     14.2                         NaN              
        0             0                   0                    -1.31                           NaN                      0                   0                     5.31                           NaN                     0                  0                       -0.27                        NaN                      5.1                 136                     60.5                         NaN              
      589          4.62                 127                     87.4                        1.4531                   4.71                 125                     85.7                        1.4586                     0                  0                      -0.212                        NaN                     4.82                 122                     79.9                         NaN              
        0             0                   0                    -1.61                           NaN                   4.71                 125                     85.7                        1.4586                     0                  0                    -0.00285                        NaN                     4.82                 122                       79                         NaN              
      523           4.6                 114                    -1.47                           NaN                    4.6                 114                     47.8                        2.3849                     0                  0                      -0.401                        NaN                      5.8                90.2                     1.99                         NaN              
      597          6.78                  88                    -1.32                           NaN                   6.96                85.8                     49.5                        1.7333                     0                  0                      -0.428                        NaN                     7.21                82.8                     32.7                         NaN              
      597          6.78                  88                     76.8                        1.1458                   6.96                85.8                     72.6                        1.1818                     0                  0                      -0.158                        NaN                        0                   0                    0.357                         NaN              

PEM1b = '0001';

indx = ~isnan(newTable.PEM1_GA_Current_Estimate_Error);
temp = repmat({'0000'},size(newTable,1),1);
temp(indx) = {PEM1b}

temp = 2609x1 cell array
    {'0000'}
    {'0000'}
    {'0001'}
    {'0001'}
    {'0000'}
    {'0001'}
    {'0001'}
    {'0001'}
    {'0000'}
    {'0000'}
    {'0000'}
    {'0001'}
    {'0000'}
    {'0000'}
    {'0000'}
    {'0001'}
    {'0000'}
    {'0001'}
    {'0000'}
    {'0000'}
    {'0000'}
    {'0000'}
    {'0001'}
    {'0001'}
    {'0001'}
    {'0001'}
    {'0001'}
    {'0001'}
    {'0001'}
    {'0001'}

%...and add this array as a new column to the table
newTable.newColumn = temp

newTable = 2609x18 table
    LPE_VBAT    PEM1_LPE_ZM    PEM1_LPE_EXP_GA_CURR    PEM1_INVERTER_CURRENT    PEM1_GA_Current_Estimate_Error    PEM2_LPE_ZM    PEM2_LPE_EXP_GA_CURR    PEM2_INVERTER_CURRENT    PEM2_GA_Current_Estimate_Error    PEM3_LPE_ZM    PEM3_LPE_EXP_GA_CURR    PEM3_INVERTER_CURRENT    PEM3_GA_Current_Estimate_Error    PEM4_LPE_ZM    PEM4_LPE_EXP_GA_CURR    PEM4_INVERTER_CURRENT    PEM4_GA_Current_Estimate_Error    newColumn
    ________    ___________    ____________________    _____________________    ______________________________    ___________    ____________________    _____________________    ______________________________    ___________    ____________________    _____________________    ______________________________    ___________    ____________________    _____________________    ______________________________    _________

        0             0                   0                    -1.43                           NaN                      0                   0                     9.73                           NaN                     0                  0                      -0.478                        NaN                     5.41                 129                      109                         NaN                  {'0000'} 
      530          4.21                 126                     2.62                           NaN                   4.65                 114                     46.7                        2.4411                     0                  0                      -0.356                        NaN                     5.06                 105                     1.97                         NaN                  {'0000'} 
      530          4.21                 126                     66.3                        1.9005                      0                   0                   -0.343                           NaN                     0                  0                      -0.546                        NaN                     5.06                 105                     57.7                         NaN                  {'0001'} 
      531          4.91                 108                     97.4                        1.1088                   4.49                 118                      109                        1.0826                     0                  0                        -1.1                        NaN                     4.19                 127                      110                         NaN                  {'0001'} 
      590          4.62                 128                    -1.27                           NaN                    5.3                 111                     65.3                        1.6998                     0                  0                      -0.515                        NaN                     5.26                 112                     35.8                         NaN                  {'0000'} 
      535          5.76                  93                     39.7                        2.3426                    5.3                 101                     66.9                        1.5097                     0                  0                      -0.171                        NaN                     5.06                 106                     3.26                         NaN                  {'0001'} 
      535          5.76                  93                     82.1                        1.1328                    5.3                 101                       91                        1.1099                     0                  0                      -0.222                        NaN                        0                   0                    0.454                         NaN                  {'0001'} 
      524          5.93                88.4                     76.3                        1.1586                   6.45                81.2                     73.7                        1.1018                     0                  0                      -0.761                        NaN                     6.25                  84                     69.8                         NaN                  {'0001'} 
      589          5.33                 110                     3.21                           NaN                      0                   0                   0.0767                           NaN                     0                  0                      -0.152                        NaN                     4.99                 118                     36.7                         NaN                  {'0000'} 
        0             0                   0                    -1.37                           NaN                      0                   0                     5.44                           NaN                     0                  0                     -0.0206                        NaN                        5                 138                     14.2                         NaN                  {'0000'} 
        0             0                   0                    -1.31                           NaN                      0                   0                     5.31                           NaN                     0                  0                       -0.27                        NaN                      5.1                 136                     60.5                         NaN                  {'0000'} 
      589          4.62                 127                     87.4                        1.4531                   4.71                 125                     85.7                        1.4586                     0                  0                      -0.212                        NaN                     4.82                 122                     79.9                         NaN                  {'0001'} 
        0             0                   0                    -1.61                           NaN                   4.71                 125                     85.7                        1.4586                     0                  0                    -0.00285                        NaN                     4.82                 122                       79                         NaN                  {'0000'} 
      523           4.6                 114                    -1.47                           NaN                    4.6                 114                     47.8                        2.3849                     0                  0                      -0.401                        NaN                      5.8                90.2                     1.99                         NaN                  {'0000'} 
      597          6.78                  88                    -1.32                           NaN                   6.96                85.8                     49.5                        1.7333                     0                  0                      -0.428                        NaN                     7.21                82.8                     32.7                         NaN                  {'0000'} 
      597          6.78                  88                     76.8                        1.1458                   6.96                85.8                     72.6                        1.1818                     0                  0                      -0.158                        NaN                        0                   0                    0.357                         NaN                  {'0001'} 

[Jorge]

yes! I found out about the isnan after the fact. Thanks as always for your great help.

Answer 1

[Stephen23]

"I don't think I should need a for loop to iterate through each row and replace the value at the "indx" location"

You do not need a loop, just assign a scalar cell array to the existing cell array using parentheses:

temp(indx) = {PEM1b};

"what am I doing wrong?"

You are trying to assign one array to multiple cells of the cell array. You could think of it something like this:

[a,b,c,d,e,f,..] = pi

While this might be a defined syntax in some languages, with MATLAB this does not assign one array to lots of cells (or variables or fields or ...). In general it is an error. You could use DEAL for some of those situations, but your usecase is actually much simpler: you can use the special case that applies for any array type: a scalar on the RHS will always be expanded to fit the indexing on the LHS into an array of the same type. So all you need is a scalar cell array on the RHS. Which means that the LHS must use parentheses to assign to the cell array itself, not curly braces to replace its content. Then you assign a scalar array element on the RHS to as many elements on the LHS as the indexing specifies (note how I did not write cell, because this concept is exactly the same for every array class).

[Stephen23]

C = num2cell('a':'i')

C = 1x9 cell array
    {'a'}    {'b'}    {'c'}    {'d'}    {'e'}    {'f'}    {'g'}    {'h'}    {'i'}

C([2,8]) = {'xxx'} % assign scalar to array

C = 1x9 cell array
    {'a'}    {'xxx'}    {'c'}    {'d'}    {'e'}    {'f'}    {'g'}    {'xxx'}    {'i'}

[C{[3,7]}] = deal('yyy') % comma-separated list

C = 1x9 cell array
    {'a'}    {'xxx'}    {'yyy'}    {'d'}    {'e'}    {'f'}    {'yyy'}    {'xxx'}    {'i'}

C{[4,6]} = 'zzz' % error

Assigning to 2 elements using a simple assignment statement is not supported. Consider using comma-separated list assignment.

[Jorge]

I could have sworn I tried that! Thank you!

[Jorge]

ah...this is the error I got when I had tried that before:

Conversion to char from cell is not possible.

Error in ProcessLPEfieldData (line 97)
temp(indx) = {PEM1b}

[Jorge]

here's the code...

% Compute actual vs. estimate error, add to table for each PEM
% PEM1
errorarray= newTable.PEM1_LPE_EXP_GA_CURR./newTable.PEM1_INVERTER_CURRENT;
newTable = addvars(newTable,errorarray,'NewVariableNames','PEM1_GA_Current_Estimate_Error','After',4)

% PEM2
errorarray= newTable.PEM2_LPE_EXP_GA_CURR./newTable.PEM2_INVERTER_CURRENT;
newTable = addvars(newTable,errorarray,'NewVariableNames','PEM2_GA_Current_Estimate_Error','After',8)

% PEM3
errorarray= newTable.PEM3_LPE_EXP_GA_CURR./newTable.PEM3_INVERTER_CURRENT;
newTable = addvars(newTable,errorarray,'NewVariableNames','PEM3_GA_Current_Estimate_Error','After',12)

% PEM4
errorarray= newTable.PEM4_LPE_EXP_GA_CURR./newTable.PEM4_INVERTER_CURRENT;
newTable = addvars(newTable,errorarray,'NewVariableNames','PEM4_GA_Current_Estimate_Error','After',16)

% Clean up Data
indx =find(newTable.PEM1_INVERTER_CURRENT < 10);
newTable.PEM1_GA_Current_Estimate_Error(indx) = NaN;

indx =find(newTable.PEM2_INVERTER_CURRENT < 10);
newTable.PEM2_GA_Current_Estimate_Error(indx) = NaN;

indx =find(newTable.PEM3_INVERTER_CURRENT < 10);
newTable.PEM3_GA_Current_Estimate_Error(indx) = NaN;

indx =find(newTable.PEM4_INVERTER_CURRENT < 10);
newTable.PEM4_GA_Current_Estimate_Error(indx) = NaN;

% Errors based on Complement of PEMs active
PEM1b ='0001';
PEM2b ='0010';
PEM3b = '0100';
PEM4 = '1000';

%save([datapath 'data.mat'],'newTable')
temp=[];
indx=(find(newTable.PEM1_GA_Current_Estimate_Error ~= NaN))
temp =[repmat('0000',size(newTable,1),1)]
temp(indx) = {PEM1b}
newTable=addvars(newTable,temp,'NewVariableNames', 'Module 1', 'After',1)

[Stephen23]

What you showed in your question:

temp={};
temp ={repmat('0000',size(newTable,1),1)}

What you showed in your comment:

temp=[];
temp =[repmat('0000',size(newTable,1),1)]

They are completely different things:

• in your question you create a cell array (which is a container array) and put things into it.
• in your comment you create a character matrix (which is NOT a container array).

I could give you a box with an apple in it. Or I could give you an apple. But they are not the same thing: you cannot have a command which says "replace the content of the apple with a banana". But you can do that with the box.

A table is a container array, it may contain a character matrix. So from that point of view, you could use either.

But if you use a character matrix then you need to use parentheses indexing to refer to those characters themselves (not some inappropriate curly-brace indexing as if those characters were stored inside containers, which in your comment they are not). Using the character matrix will be more effort because you are not allocating a scalar array on the RHS, you are now attempting to allocate a vector (i.e. multiple elements) which means that you will need the number of elements on the LHS and the RHS to match exactly, which will mean that you will need to use e.g. REPMAT or similar on the RHS. You will most likely need to use subscript indexing or perform some conversion to linear indexing, which would take a few lines of code... and so your code will be more complex and more liable to bugs...

It would be simpler to stick with a cell array of character vectors, just like you showed in your question.

Or perhaps even better, a string array.

Also: if you use a character matrix get rid of those superfluous square brackets:

temp=[]; % <- this does nothing, get rid of it.
temp =[repmat('0000',size(newTable,1),1)]
%     ^  superfluous, get rid of them   ^

[Jorge]

thank you for the detailed explanation. Much appreciated! I ended up going with the string array. However, I don't fully understand this....I first tried

temp=[];
indx=find(not(isnan(newTable.PEM1_GA_Current_Estimate_Error)));
temp =repmat("0000",size(newTable,1),1);
temp(indx) = {char(PEM1b)};
newTable=addvars(newTable,temp,'NewVariableNames', 'Module 1', 'After',1)

which seemed to work. But I didn't understand why it would....

I ended up with

temp(indx) = PEM1b

which to me makes more sense. can you explain what I "did" here? maybe this will help me get it!

thanks!

[Stephen23]

"which seemed to work. But I didn't understand why it would...."

Unlike some other languages, type coercion in MATLAB was in the past basically limited to the numeric types and char. For better or for worse, modern users apparently expect type coercion between everything, so the (relatively new) string class can coerce numeric, char, and cell-of-char into strings:

S = "this" % string

S = "this"

S(2) = 'assigns' % char

S = 1x2 string array
    "this"    "assigns"

S(3) = 3 % numeric

S = 1x3 string array
    "this"    "assigns"    "3"

S(4) = {'types'} % cell of char

S = 1x4 string array
    "this"    "assigns"    "3"    "types"

"which to me makes more sense. can you explain what I "did" here?"

You created a string array and then assigned a character vector to it, which got coerced into a string:

T  = ["hello";"x"]

T = 2x1 string array
    "hello"
    "x"

T(2) = 'world'

T = 2x1 string array
    "hello"
    "world"

Using a scalar string on the RHS would not use any coercion.

[Jorge]

I really appreciate you taking the time to explain. I get it now. Thank you!