How can I group data points together

[Image Analyst]

Why did you delete your question?

[Rik]

I don't seem to be able to make a capture of the cache, but here is the content anyway:

I need to "bin" data points together into one number. This file has 70,000 lines of data points, in unevenly spaced, often repeating increments. For example, I need to average all the different numbers (2.419, 2.417, 2.405, etc...) with decimals into 2.000.

[Matthew Suddith]

Thank you! I meant to edit it but I completely deleted it and couldnt figure out how to get it back.

Answer 1

[Cris LaPierre]

It doesn't sound like you want to average them. For the example you've given, why not just round the numbers down to 2? The functions round, ceil, floor and fix might be of interest to you.

vals = [2.419, 2.417, 2.405];
round(vals)

ans = 1×3

2 2 2

ceil(vals)

ans = 1×3

3 3 3

●

floor(vals)

ans = 1×3

2 2 2

●

fix(vals)

ans = 1×3

2 2 2

[Matthew Suddith]

The numbers are the depth at which the measurements were taken, and have associated calculations with them in 30 columns. I need to average each different depth, and its associated calculations, into a single depth so that I have one value at each depth. So 2.4100 m, 2.400m, etc is 2.000 m

[Cris LaPierre]

For those of us not familiar with your data, how would we know what values to use?

[Matthew Suddith]

What values do you need, I need to a function to average each decimal depth into a single 2.000 depth

[Cris LaPierre]

I would think a better undertanding of what your data looks like would greatly faciliate proposing a solution. You can attach a sample of your data using the paperclip icon.

Absent that, I would encourage you to look at the documentation for groupsummary. You can average your data by groups you specify.

[Matthew Suddith]

Here is a small snapshot of the data file. The depths range to the 700s, then return all the way back to the starting depth

[Matthew Suddith]

the depth is the first value on the left

[Cris LaPierre]

Ok, so for the solution I'm thinking about to work, i would need to create an "actual depth" column that would take your values and bin them to the corresponding actual value. Could you tell us what the actual depths should be? How much does the values in the file vary from the actual depths?

Any chance you can upload an actual text file of your data? I'm not feeling motivated enough to transcribe the values in the png. I believe the upload has to be less that 5MB, so you can delete some rows if necessary. It would be nice to see at least a couple of the different depths in the file.

[Matthew Suddith]

Here's the problem, the actual text file is 70,000 lines, so attached is a small sample of depths 1.988 to 6.811. So then, the final product for those depths would need to look like the finalproduct txt file

[Matthew Suddith]

The txt file has that many points for each depth, all the way up to 750, then it repeats in descending order back to the first depth. Its a CTD file, it collects data at each depth as it is lowered into the ocean, then again on the way up

[Matthew Suddith]

Open this file instead for the sample, that previously linked file looks strange

[Cris LaPierre]

Ok, so now it's just about developing an algorithm for turning recorded depth into standard depths. Since no guidance has been given on how to do that, I defer to my original answer. Here's some sample code that uses the round function.

data = readtable("sample.txt");
data.Properties.VariableNames(1) = "Depth";
% Create groups by rounding the depths to integer values
data.grpDepth = round(data.Depth);

newData = groupsummary(data,"grpDepth","mean")

newData = 6x31 table
    grpDepth    GroupCount    mean_Depth    mean_Var2    mean_Var3    mean_Var4    mean_Var5    mean_Var6    mean_Var7    mean_Var8    mean_Var9    mean_Var10    mean_Var11    mean_Var12    mean_Var13    mean_Var14    mean_Var15    mean_Var16     mean_Var17     mean_Var18    mean_Var19    mean_Var20    mean_Var21    mean_Var22    mean_Var23    mean_Var24    mean_Var25    mean_Var26    mean_Var27    mean_Var28    mean_Var29 
    ________    __________    __________    _________    _________    _________    _________    _________    _________    _________    _________    __________    __________    __________    __________    __________    __________    ___________    ___________    __________    __________    __________    __________    __________    __________    __________    __________    __________    __________    __________    ___________

       2            38          2.0818       32.252       14.397       0.13886       1.014       5.9752        260.6       101.96       5.8557        255.39         213.7      0.00020461       2.115        32.252        14.397       6.5789e-05    -0.00016055      246.76        39337         37267        -0.10753        1024         23.982        14.397        4.4036       0.22415       0.19865        3.0578        -9.99e-29
       3            31          3.0398       32.252       14.397       0.13741      1.0094       5.9737       260.54       101.94       5.8557        255.39        152.62       0.0002013      3.0614        32.252        14.397      -0.00012905    -0.00024194      246.76        39338         38069        -0.35504        1024         23.982        14.397        4.4052        0.2218       0.19815        2.9156      -3.2226e-30
       4            98          3.8058       32.252       14.398       0.13692       1.052       5.9826       260.93       102.09       5.8556        255.39        131.18      0.00019675      3.8405        32.252        14.398       7.3469e-05    -0.00035509      246.76        39339         32514        -0.31612        1024         23.982        14.397        4.4057       0.21853       0.20287        2.8509      -6.3202e-29
       5            32          5.0267       32.252       14.397       0.13738      1.0955         5.99       261.25       102.22       5.8556        255.39         110.7      0.00019822      5.0663        32.252        14.398           0.0004     -0.0004125      246.76        39339         35651        -0.09156        1024         23.982        14.397        4.4052       0.21957       0.20769        2.7771                0
       6            76          6.0728       32.252       14.397       0.13706      1.1068       5.9849       261.03       102.13       5.8556        255.39         91.28      0.00019676      6.1242        32.252        14.397       0.00010393    -0.00041053      246.76        30540         36233        -0.35731        1024         23.982        14.396        4.4056       0.21853       0.20898        2.6938      -3.1547e-29
       7            13          6.6319       32.252       14.367       0.13656      1.0951       5.9974       261.57       102.34       5.8556        255.39        89.053      0.00019123      6.6817        32.252        14.397       0.00018333     -0.0004166      246.76        39340         39340        -0.28558        1024         23.982        14.396        4.4061       0.21462       0.20768        2.6834                0

[Matthew Suddith]

Thank you so much, that looks like it could work for what I need to do! But I get this error message: "Error using round

First argument must be a numeric, logical, or char array."

[Matthew Suddith]

When I subsitute the "sample.txt" with the actual file

[Matthew Suddith]

Also, when this creates a table, would I be able to turn that table back into a txt file?

[Cris LaPierre]

This likely means at least one of your depth values contains a value that cannot be rounded. Does one of the rows contain a non-numeric value? Does it work with a subset of the actual data?

To your second question, yes. Look at writetable.

[Matthew Suddith]

Ok, yes the problem is the actual data file has a header on top that isnt numbers. So I need to make it read the file, but beginning at a certain line: needs to start at line 365.

[Cris LaPierre]

Do any of those header lines contain variable names identifying what is in each column?

[Matthew Suddith]

Yes they do, they identify what is in each column

[Cris LaPierre]

Which line has that info? Line 364?

[Matthew Suddith]

this is the header, copied from the actual file

[Cris LaPierre]

There are 10 rows unaccounted for. This head has 354 rows of data, but you mentioned the numbers start at row 365. Are there blank rows between the header and the first row of numbers? Could you attach a subset of your data file containing the first 1000 rows including the header?

[Matthew Suddith]

Sorry, it actually starts at 355. Here is the first 1000

[Cris LaPierre]

There are numerous ways to do this, but probably the easiest to understand is this.

data = readtable("first1000.txt",'NumHeaderLines',354,"MultipleDelimsAsOne",true,"LeadingDelimitersRule","ignore");
data.Properties.VariableNames(1) = "Depth";
% Create groups by rounding the depths to integer values
data.grpDepth = round(data.Depth);

newData = groupsummary(data,"grpDepth","mean")

[Matthew Suddith]

That worked with the complete file, I hate to keep asking you questions, but how would I then change the name of each mean_variable# column header to the variable it is supposed to be?

[Cris LaPierre]

This has to be done manually. Using the names I see in the header, something like this at the end should do it.

newData.Properties.VariableNames(3:end) = ["depSM","sal00","t090C","CStarAt0",...
    "flECO-AFL","sbeox0ML/L","sbox0Mm/Kg","sbeox0PS","oxsatML/L","oxsatMm/Kg",...
    "par","turbWETbb0","prDM","sal11","t190C","T2-T190C","secS-priS","timeJ",...
    "c0uS/cm","c1uS/cm","C2-C1uS/cm","density00","sigma-theta00","potemp090C",...
    "v4","v3","v2","v5","flag"]

As for accessing data in a table, see this page.

[Cris LaPierre]

WRT the questions asked here

I really don't have enough information to answer that question. What file are you comparing it to? How were the data grouped and averaged in that file?

You could try using a method other than round.

I'm not sure how using a for/while loop helps you here.

[Matthew Suddith]

The file that I'm comparing it to is the "binned" version of the file I showed you, the one with the 70,000 lines. But I don't know how it was grouped and averaged. I'm happy with the rounding method you showed me, I really appreciate your help. I may continue posting a few more tiny questions, but I don't expect you to answer all night.

[Cris LaPierre]

Try using fix (assigns 2-2.9 a value of 2) or ceil (assigns 2.01-3 a vaue of 3) instead of round. It's a simple change to make to the code, and together form the 3 most likely methods used.

[Matthew Suddith]

When using writetable, how can you outfile it to a text document

[Matthew Suddith]

so replacing round(data.Depth) with one of those gives me an error on the = both ways

[Cris LaPierre]

Round, ceil, fix and floor all worked for me. I think you have a syntax error. I suggest reading the documentation I linked to previously to see how to use them. You should just have to replace "round" in the current code with "ceil", for example.

Yes, it is possible to use writetable to save a table to a text file. Again. read the documentation I linked to previously to see how to do it.

[Matthew Suddith]

Is there a way to format the output of writetable, because on the txt file it outputs it is a big jumbled mess

[Cris LaPierre]

It looks like by default it writes a csv file. You could look at the name-value pairs for what options are available.

For more control, fprintf may be what you need.

[Matthew Suddith]

That worked. How could I plot my rounded data and the original data in one plot for a direct comparison, is that doable?

[Cris LaPierre]

Ch 9 of MATLAB Onramp.