How to create the "for" loop?

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Rahul Verma
Rahul Verma on 10 Apr 2023
Commented: Dyuman Joshi on 10 Apr 2023
I am trying to create 'for' loop for one easy problem. It is a simple subsraction.
Let me explain more about. So i want to calculate "v" by using this formula; v = datainput - XSS
Here, the size of datainput is 34*36 and size of XSS is 34*1296.
Now, the trick is that when the substraction takes place, it should be in a manner that 1st column of datainput - /minus whole XSS, (which will give a matrix of size 34*1296). Likewise for whole 36 columns the substraction should happen. And the final result should be stored in v (of size 34*36*1296).
For this i am attaching the datainput and XSS excel files.

Answers (1)

Dyuman Joshi
Dyuman Joshi on 10 Apr 2023
Edited: Dyuman Joshi on 10 Apr 2023
Loop approach
datainput=rand(34,36);
XSS=rand(34,1296);
%Preallocation
v=zeros(34,36,1296);
for k=1:size(datainput,2)
v(:,k,:)=datainput(:,k)-XSS;
end
Vectorized approach -
V=datainput-permute(XSS,[1 3 2]);
%Ideally one should you tolerance to compare floating point numbers
isequal(v,V)
ans = logical
1
  2 Comments
Rahul Verma
Rahul Verma on 10 Apr 2023
In both appraoches, its showinng error. Size of matrix is not matching.
Dyuman Joshi
Dyuman Joshi on 10 Apr 2023
It's working fine here. How are you importing your data?
XSS=readmatrix('XSS.xlsx');
size(XSS)
ans = 1×2
34 1296
datainput=readmatrix('datainput.xlsx');
size(datainput)
ans = 1×2
34 36
v=zeros(34,36,1296);
for k=1:size(datainput,2)
v(:,k,:)=datainput(:,k)-XSS;
end
V=datainput-permute(XSS,[1 3 2]);
isequal(v,V)
ans = logical
1

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