ned to turn iterated columns into a single column

I havea code that takes data from multiple matlab files and then created about output data of it. The problem is that the data is in separate columns per matlab file input. I want them to all be on one column

For example the first input is 50x1, the next is 100x1, then 22 x1. (the data amount will be different every time). I want these to be 177x1

This is the current codethat I have:

%% Pre-allocate memory for group data
GroupData.SubjectList = subjlist;
GroupData.Interval = NaN(length(subjlist));
 
%% Collect individual data and put into structure
for iteration = 1:length(subjlist)
 
    if subjlist (iteration, 1)<100
    SubjectData = sprintf('load NCL0%d_Session00%d.mat',subjlist(iteration,1), subjlist(iteration,2));
    eval(SubjectData);
    else
    SubjectData = sprintf('load NCL0%d_Session0%d.mat', subjlist(iteration,1), subjlist(iteration,2));
    eval(SubjectData);
    end
    
    RawHoldTime= (Poke_HoldData(:,10))
    %[ data_output ] = HoldTime_RawHoldTime( Poke_HoldData )
    GroupData.RawHoldTime(:,iteration) = RawHoldTime;
    
    %% combining into 1 column
 
 
end
 
end

Answer 1

[Stephen23]

Do NOT use EVAL for trivial code like this. Rather than forcing yourself into writing complex, obfuscated code just because you want to use command syntax, you should always prefer to use function sytnax:

https://www.mathworks.com/help/matlab/matlab_prog/command-vs-function-syntax.html

For example, replace this obfuscated code:

SubjectData = sprintf('load NCL0%d_Session%03d.mat',subjlist(iteration,1), subjlist(iteration,2));
eval(SubjectData);

with this simpler, cleaner, more efficient code:

F = sprintf('NCL%02d_Session%03d.mat',subjlist(iteration,1:2));
S = load(F); % <- function syntax!

Note how I also loaded into an output variable S (which is a scalar structure) to make the code much more robust.

Rather than duplicating code inside that IF-ELSE and adding those leading zeros by hand, you should use the SPRINTF fieldwidth and leading zeros options to specify the number of leading zeros, as my code above shows.

A robust and efficient way to create one vector as you request from the imported data of multiple files is to concatenate the imported data after the loop. This is very easy to achieve using a comma-separated list:

N = size(subjlist,1); % SIZE is reliable, LENGTH is not.
C = cell(1,N); % preallocate
for k = 1:N
    F = sprintf('NCL%02d_Session%03d.mat',subjlist(k,1:2));
    S = load(F);
    C{k} = S.Poke_HoldData(:,10);
end
V = vertcat(C{:}) % <- comma-separated list

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

Note that you can easily process files that are lcoated in another directory (separate your code and data!):

P = 'absolute or relative path to the folder where the files are saved';
..
for k = 1:N
    ..
    S = load(fullfile(P,F));
    ..
end

[Phoebe Langius]

As I am new to matlab i am a bit confused. In the pokeholdData I am trying to take raw poke hold time (which is the tenth column of pokehold data). Im trying to take multiple files of this and combine all of the column 10s into a single column. If I replace my current code with these two I still get an error an unregonized function or variable iteration. How is this possible and what can I do to fix it?

[Phoebe Langius]

Why also in your code is NCL%02d_Session%03d.mat with 2 and 3? my data for NCL is from 243-252 and 280-289. The sessions go from 001 to the 300s. COuld you further explain this?

[Stephen23]

"If I replace my current code with these two I still get an error an unregonized function or variable iteration. How is this possible and what can I do to fix it? "

The only part of my answer that you need to use is the code

N = ..
..
V = ..

It contains the loop and concatenates the data into one vertical column V.

"Why also in your code is NCL%02d_Session%03d.mat with 2 and 3?"

As I wrote in my answer, this uses the SPRINTF fieldwidth and leading zeros options to specify the number of leading zeros that those integers use:

... NCL%02d_Session%03d.mat
...    %  d                 Integer field.
...     0                   Pad to field width with zeros before the value.
...      2                  Minimum field width.

https://www.mathworks.com/help/matlab/ref/sprintf.html#btf_bfy-1_sep_shared-formatSpec

Thus we can trivially avoid your duplicated code and IF-ELSE.

[Phoebe Langius]

ok I see what you mean, thank you! but I still get the following error.

Unrecognized function or variable 'iteration'.

Error in GroupAnalysis_RawHoldTime (line 26)

F = sprintf('NCL%02d_Session%03d.mat',subjlist(iteration,1:2));

[Stephen23]

"I still get the following error."

Unrecognized function or variable 'iteration'.
...
    F = sprintf('NCL%02d_Session%03d.mat',subjlist(iteration,1:2));

That line of code does not exist within the parts of my answer that I told you to copy.

Here is the complete code that you need, copied verbatim from my answer:

N = size(subjlist,1); % SIZE is reliable, LENGTH is not.
C = cell(1,N); % preallocate
for k = 1:N
    F = sprintf('NCL%02d_Session%03d.mat',subjlist(k,1:2));
    S = load(F);
    C{k} = S.Poke_HoldData(:,10);
end
V = vertcat(C{:}) % <- comma-separated list

Note that unlike your error message, my code does not contain any variable named iteration. For some reason you appear to be combining together examples from my answer, which is unlikely to work.

[Phoebe Langius]

I am not completely understanding. If I add this to my current code it will not work, but if I delete it all and only add this, this the S = load(F); is causing an error. if I add the code above as well as

F = sprintf('NCL%02d_Session%03d.mat',subjlist(iteration,1:2));

S = load(F); % <- function syntax!

I get the iteration error.

I appraciate you helping me with this as this is my first code and I apologize for the confusion regaridng it.

[Stephen23]

"If I add this to my current code it will not work..."

The code I gave you to use, from

N = ...
.. to
V = ...

does not get "added" to your current code. It replaces it.

• Your code has a loop.
• My code has a loop.
• Your code generates some filenames.
• My code generates some filenames.
• Your code loads filedata.
• My code loads filedata.
• My code concatenates the filedata into one vector.

For some reason you keep quoting lines of code from my answer that are examples that I used to explain particular features or syntax. But none of the lines of code you have so far shown in any of these comments are actually the code that I wrote that you should use.

I already explained that in my previous comment, complete with a verbatim copy of the complete code that I wrote for you to try. Would you like to try it?

[Phoebe Langius]

So I deletedevetythig and only put in your code. I get this error even though the files are added to the path.

[Phoebe Langius]

I chose a small subjlist first to see if it would work

[Stephen23]

Judging by those filenames, you should set the first fieldwidth to 4:

... 'NCL%04d_Session%03d.mat'
...       ^

Answer 2

[Phoebe Langius]

I have figured it out! Thank you so much!

[Stephen23]

I am glad that you got it working.

Please remember to accept and/or vote for my answer if it helped you.