How to assign variable names and import data via loop?

Hi all,

I have recently completed an assignment where I was required to plot graphs of various soil tests. The data from the tests was stored in .csv files, I've imported the files using xlsread but for each test, I simply copy and pasted the code to import the data. This was OK for the purposes of this assignment, but how can I make it more efficient for future assignments? An example of how have done the assignment is as follows:

 %%Data import 
%Test 1 10kg
t1 = xlsread('group21.csv', 'A4:A1216')'; %  Seconds 
t1(find(t1>200)) = NaN;
L1 = abs(xlsread('group21.csv', 'B4:B1216'))'; %  Newtons 
s1=L1./(0.1*0.1); %  Pascals 
d1= xlsread('group21.csv', 'C4:C1216')'; % Micro Meters

This was repeated (copy and pasted) for FIVE tests. How can I write it in a loop such that I can get it to output t1,t2,....,L1,L2... etc by simply typing t1 in the command window? I want it to just display that variable t1.

Further more I then plotted these as follows:

 figure('Color', [1 1 1]) 
hold on 
grid on
grid minor

 plot(t1.*(1/30),s1,'.r') 
plot(t2.*(1/30),s2, '.b') 
plot(t3.*(1/30),s3, '.g') 
plot(t4.*(1/30),s4, '.m') 
plot(t5.*(1/30),s5, '.k')

How could I automate it so I can type plot(something here to make it plot all t1 t2 etc, something here to plot s1 s2 etc) ?

Any assistance would be appreciated as I feel copying and pasting the code for each test is beginning to create more problems than it solves as I conduct more complicated tests as my degree progresses.

Thanks in advance.

Answer 1

[Star Strider]

A loop with a cell array would likely work:

for k1 = 1:5
    t{k1} = xlsread('group21.csv', 'A4:A1216')'; %  Seconds
    t{k1}(t{k1}>200) = NaN;
    L{k1} = abs(xlsread('group21.csv', 'B4:B1216'))'; %  Newtons
    s{k1}=L{k1}./(0.1*0.1); %  Pascals
    d{k1}= xlsread('group21.csv', 'C4:C1216')'; % Micro Meters
end

Note — I can test part of this but not all of it, so I am labeling it UNTESTED CODE. It should work, but without your Excel files, I can’t test it.

[Thomas Kelly]

Yeah that works great thanks. Changed it a bit but the idea you presented was pretty much what I wanted. Here is what I have now that works:

%%Import 
for k1 = 1:5
  t{k1} = xlsread(['group2', num2str(k1) '.csv'], 'A4:A1216')'; %  Seconds
  t{k1}(t{k1}>200) = NaN;
  L{k1} = abs(xlsread(['group2', num2str(k1) '.csv'], 'B4:B1216'))'; %  Newtons
  s{k1}=L{k1}./(10); %  Pascals
  %d{k1}= xlsread('group21.csv', 'C4:C1216')'; % Micro Meters
end
%Plot 
  figure('Color', [1  1 1]) 
for k1 = 1:5  
      hold on
  grid on
  grid minor
  plot(t{1,k1}./30,s{1,k1}, '.') 
  axis square
end 
xlabel('Displacement (\delta_x - mm)') 
ylabel('Shear Stress (\tau  - kPa)') 
legend('Test 1 - 10kg', 'Test 2 - 20kg','Test 3 - 30kg','Test 4 - 40kg','Test 5 - 50kg','Location', 'SouthEast')
title('Shear Stress vs Horizontal Displacement')
axis square
hold off

The result is the attached graph.

[Star Strider]

My pleasure!

Interesting plot.