apply if-else-statement to a 3D matrix

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Angelavtc
Angelavtc 2022-11-26
评论： Angelavtc 2022-11-26
Dear community,
Maybe this is a somewhat obvious question, but I have a 3D matrix with normally distributed simulations like the following:
n=10000
x1 = 75:125;
y1 = 0:40;
Qd=zeros(n,length(y1),length(x1));
for i = 1:length(x1) % mean
for j = 1:length(y1) % sd
Qd(:,i,j)=normrnd(x1(i),y1(j),n,1);
end
end
Based on this matrix, I want to create another one with 3 conditionals. If the element Qd(k,i,j) is less than 25 then the new matrix should have a 50; if it is between 25 and 50 it should give me 10; if it is greater than 50 it should give me 30. The problem is that I have tried with the following and the elseif command is not working properly :( Any hint will be really appreciated! Thank you!
Pw=zeros(n,length(y1),length(x1));
for k = 1:n
for i = 1:length(x1)
for j = 1:length(y1)
if Q_d(k,i,j)<=25
Pw(k,i,j)=50;
elseif 25<Q_d(k,i,j)<=50
Pw(k,i,j)=10;
else
Pw(k,i,j)=30;
end
end
end
end

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Dyuman Joshi
Dyuman Joshi 2022-11-26
编辑：Dyuman Joshi 2022-11-26
The syntax for comparing multiple conditions is individualistic in MATLAB, i.e. you have to write code for each condition individually -
elseif 25<Q_d(k,i,j) && Q_d(k,i,j)<=50
Edit - The pre-allocation of Pw w.r.t to the individual dimensions and the loop indices does not match
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Dyuman Joshi
Dyuman Joshi 2022-11-26
Pw=zeros(n,length(y1),length(x1));
You initialised Pw with dimensions corresponding to n, y1 and x1 respectively. However, in your loop
for k = 1:n
for i = 1:length(x1)
for j = 1:length(y1)
if Q_d(k,i,j)<=25
The respective loop variables correspond to n, x1 and y1. Which are not equal to n, y1 and x1 (order) as in the definition of Pw.
%Either you can change the order of indices
Q_d(k,j,i)
%or change the loop parameters.
I hope you get my point.

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