Sum of elements in cell array

Hi,

I have this cell array

One of its rows, look like this

I am using this code to sum the columns of each cell

Force = cellfun(@(x){sum(x(1:3:end,:)); sum(x(2:3:end,:))}, Numerical, 'Uni',0);

But I am not getting correct result , because when I add them manually, I get this ( only for the first row of Numerical{4,1} )

ans =

   0.0000e+00 - 1.0232e-12i
   

But I am getting this( only for the first row of Numerical{4,1} ) :

-1.13686837721616e-13 - 2.27373675443232e-13i

I am attaching the file with the question.

Does anyone know...?

[KSSV]

Your each cell has 2*3 complex matrix....what you want to add in there?

[Chris Dan]

I want to add all the columns of the matrix and then take the absolute value of them

Answer 1

[Sriram Tadavarty]

Hi Hamzah,

The issue you observe in numerical values is due to the precision that is not observed for the values.

When the format long is used, you can see what the actual values are. The decimal points up to 15 digits provide the precise results in MATLAB.

You can observe the values you calculated if you round the values to 2 decimal digits. Also, the code you are trying is to sum over the rows, rather than columns.

Implies, for all the expected output, perform as such:

cellfun(@(x) sum(round(x,2),2),Numerical,'UniformOutput',false) % If you replace the round(x,2) directly with x, it is same as you are doing

Hope this helps.

Regards,

Sriram

Answer 2

[KSSV]

Better use loop to avoid confusion using cellfun. Note cellfun also use loop inside.

clc; clear all ;
load("numerical.mat"); 
[m,n] = size(Numerical) ;
iwant = cell(m,1) ; 
for i = 1:m
  iwant{i} = abs(sum(Numerical{i})) ; 
end

[Chris Dan]

KSSV

This code is giving wrong answers...

one of the cells ( Numerical{3,1} is this

and the answer which I am getting from the code is

It is not correct.

Can you please look into it.

[Chris Dan]

It should be

-2999.9805

2126.49999