Help with looping variables
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Mikkel Eskildsen
il 5 Nov 2018
Commentato: Image Analyst
il 7 Nov 2018
Hi guys!
I have run into problems when I try to make a loop create variables and I am not very advanced in matlab. Here is what I am trying to do:
I have a .csv-file containing columns with data, each called test1, test2 and so forth. For each column, I am trying to create a variable in matlab - something like:
for i = 1:10
test(i) = csvvariable(:,i)
end
What I have done so far is manually creating a variable for each column in the .csv-file:
rfdtest = csvread('Hamstring.csv', 8, 1);
test1 = rfdtest(:,1);
if test1(1)>0
test1=[0;test1]
end
test2 = rfdtest(:,2);
if test2(1)>0
test2=[0;test2]
end
test3 = rfdtest(:,3);
if test3(1)>0
test3=[0;test3]
end
test4 = rfdtest(:,4);
if test4(1)>0
test4=[0;test4]
end
test5 = rfdtest(:,5);
if test5(1)>0
test5=[0;test5]
end
test6 = rfdtest(:,6);
if test6(1)>0
test6=[0;test6]
end
test7 = rfdtest(:,7);
if test7(1)>0
test7=[0;test7]
end
test8 = rfdtest(:,8);
if test8(1)>0
test8=[0;test8]
end
test9 = rfdtest(:,9);
if test9(1)>0
test9=[0;test9]
end
test10 = rfdtest(:,10);
if test10(1)>0
test10=[0;test10]
end
Later, I am going to do some calculations on each column, so this method will result in a lot of code.
Thanks in advance and feel free to ask for additional details!
2 Commenti
Stephen23
il 5 Nov 2018
Modificato: Stephen23
il 5 Nov 2018
"I have run into problems when I try to make a loop create variables and I am not very advanced in matlab."
Magically accessing variable names is one way that beginners force themselves into writing slow, complex, buggy code that is hard to debug. Read this to know why:
The simplest alternative is to use indexing to access you data, which is neat, simple, easy to debug, and highly efficient (unlike what you are trying to do). All of the data are already trivially accessible using indexing from the variable csvvariable. Note that splitting up the data (pointlessly) duplicates it in memory.
"What I have done so far is manually creating a variable for each column in the .csv-file:"
Seems complex. Copy-and-pasting code is a sign that you are doing something wrong. Instead of copy-and-pasting code, get the computer to do it for you using loops and indexing. Copy-and-pasting causes bugs (e.g. your code repeating exactly the same test) and bloats the code.
Risposta accettata
Image Analyst
il 5 Nov 2018
8 Commenti
Image Analyst
il 7 Nov 2018
You can do
for k = 1 : 10
thisColumn = rfdtest(:, k);
if thisColumn(1) ~= 0
thisColumn = [0; thisColumn];
end
% Now do something with thisColumn. Probably no need to store it for use after the loop.
end
Again, no inefficient cell arrays needed unless for some reason you need to keep/store all the individual columns after the loop ends, which you haven't shown any need for.
If you do, you'd to this:
ca = cell(10, 1); % Preallocate a cell array
for k = 1 : 10
thisColumn = rfdtest(:, k);
if thisColumn(1) ~= 0
thisColumn = [0; thisColumn];
end
ca{k} = thisColumn; % Store in a cell array.
% Now do something with thisColumn.
end
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