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Looping num2str

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Mohammed Raslan
Mohammed Raslan on 26 Jul 2021
Answered: Steven Lord on 26 Jul 2021
Assuming y = [1,2,3,4]
If I want to add a percentage to each value, I attempt to do for loop as such:
for i = 1:4
x(i) = [num2str(y(i)),'%']
But it doesn't work. However if I avoid the for loop and simply do:
x1 = [num2str(y(1)),'%']
x2 = [num2str(y(2)),'%']
x = {x1,x2,x3,x4,x5}
It works just fine. What is the problem in the for loop?

Answers (2)

Steven Lord
Steven Lord on 26 Jul 2021
An easier way to do this is to use a string array.
y = 1:4;
x = y + " %"
x = 1×4 string array
"1 %" "2 %" "3 %" "4 %"

James Tursa
James Tursa on 26 Jul 2021
Edited: James Tursa on 26 Jul 2021
x(i) references a single element of x. However, the expression [num2str(y(i)),'%'] generates multiple characters. In essence, you are trying to assign multiple characters to a single element, and they just don't fit. Of course, you can use cell arrays for this as you have discovered, since cell array elements can contain entire variables regardless of size or class. Using cell arrays also works in case some strings are longer than others.
Note, you could have just used the curly braces in your for loop to generate the cell array result:
for i = 1:4
x{i} = [num2str(y(i)),'%'];
Or generated the cell array result directly with arrayfun:
x = arrayfun(@(a)[num2str(a),'%'],y,'uni',false);

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