How can I run a MATLAB script on .csv files in two separate folders at the same time? - matlab

Question

So I have an iterative loop that extracts data from .csv files in MATLAB's active folder and plots it. I would like to take it one step further and run the script on two folders, each with their own .csv files.
One folder is called stress and the other strain. As the name implies, they contain .csv files for stress and strain data for several samples, each of which is called E3-01, E3-02, E3-03, etc. In other words, both folders have the same number of files and the same names.
The way I see it, the process would have the following steps:
Look in the stress folder, look inside file E3-01, extract the data in the column labelled Stress
Look in the strain folder, look inside file E3-01, extract the data in the column labelled Strain
Combine the data together for sample E3-01 and plot it
Repeat steps 1-3 for all files in the folders
Like I said, I already have a script that can find the right column and extract the data. What I'm not sure about is how to tell MATLAB to alternate the folder that the script is being run on.
Instead of a script, would a function be better? Something that accepts 4 inputs: the names of the two folders and the columns to extract?
EDIT: Apologies, here's the code I have so far:
clearvars;
files = dir('*.csv');
prompt = {'Plot name:','x label:','y label:','x values:','y values:','Points to eliminate:'};
dlg_title = 'Input';
num_lines = 1;
defaultans = {'Title','x label','y label','Surface component 1.avg(epsY) [True strain]','Stress','0'};
answer = inputdlg(prompt,dlg_title,num_lines,defaultans);
name_plot = answer{1};
x_label = answer{2};
y_label = answer{3};
x_col = answer{4};
y_col = answer{5};
des_cols = {y_col,x_col};
smallest_n = 100000;
points_elim = answer{6};
avg_x_values = [];
avg_y_values = [];
for file = files'
M=xlsread(file.name);
[row,col]=size(M);
if smallest_n > row
smallest_n = row;
end
end
smallest_n=smallest_n-points_elim;
avg_x_values = zeros(smallest_n,size(files,1));
avg_y_values = zeros(smallest_n,size(files,1));
hold on;
set(groot, 'DefaultLegendInterpreter', 'none');
set(gca,'FontSize',20);
ii = 0;
for file = files'
ii = ii + 1;
[n,s,r] = xlsread(file.name);
colhdrs = s(1,:);
[row, col] = find(strcmpi(s,x_col));
x_values = n(1:end-points_elim,col);
[row, col] = find(strcmpi(s,y_col));
y_values = n(1:end-points_elim,col);
plot(x_values,y_values,'DisplayName',s{1,1});
avg_x_values(:,ii)=x_values(1:smallest_n);
avg_y_values(:,ii)=y_values(1:smallest_n);
end
ylabel({y_label});
xlabel({x_label});
title({name_plot});
colormap(gray);
hold off;
avg_x_values = mean(avg_x_values,2);
avg_y_values = mean(avg_y_values,2);
plot(avg_x_values,avg_y_values);
set(gca,'FontSize',20);
ylabel({y_label});
xlabel({x_label});
title({name_plot});
EDIT 2: #Adriaan I tried to write the following function to get a column from a file:
function [out_col] = getcolumn(col,file)
file = dir(file);
[n,s,r] = xlsread(file.name);
colhdrs = s(1,:);
[row, col] = find(strcmpi(s,col));
out_col = n(1:end,col);
end
but I get the error
Function 'subsindex' is not defined for values of class 'struct'.
Error in getcolumn (line 21)
y = x(:,n);
not sure why.

Answer 1

You can do both, of course, and it depends on preference mainly, provided you're the sole user of the script. If others are going to use it as well, use functions instead, as they can contain a proper help file and calling help functionname will then give you that help.
For instance:
folders1 = dir(../strain/*)
folders2 = dir(../stress/*)
for ii 1 = 1:numel(folders)
operand1 = folders1{ii};
operand2 = folders2{ii};
%... rest of script
%
% Or function:
data = YourFunction(folders1{ii},folders2{ii})
end
So all in all you can use both, although from experience I find functions easier to use in the end, as you just pass parameters and don't need to trawl through the complete code to change the parameters each run.
Additionally you can partition off small parts of your program which do a fix task. If you nest your functions, and finally call just a single function in your scripts, you don't have to look at hundreds of lines of code each time you run the script, but rather can just run a single function (which can also be inside a script or function, ad infinitum).
Finally, a function has its own scope; meaning that any variables that are in that function stay within that function unless you explicitly set them as output (apart from global variables, but those are problematic anyway). This can be a good thing, or a bad thing, depending on the rest of your code. If you function would output ~20 variables for further processing, the function probably should include more steps. It'd be a good thing if you create lots of intermediate variables (I always do), because when the function's finished running, the scope of that function will be removed from memory, saving you clear tmpVar1 tmpVar2 tmpVar3 etc every few lines in your script.
For the script the argument in favour would be that it is easier to debug; you don't need dbstop on error and can step a bit easier through the script, keeping check of all your variables. But, after the debugging has been completed, this argument becomes moot, and thus in general I'd start with writing a script, and once it performs as desired, I rework it to a function at minimal extra effort.