how to develope loop to save the 'n' elements from the vectors

Question

gourav pandey 2021-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/1453499-how-to-develope-loop-to-save-the-n-elements-from-the-vectors

评论： Matt J 2021-9-15

clc;

clear;

A= [14,51,2,15,........,7 ] % this is known

p1=A[1]

p2=A[2]

.

pn=A[n]

%%% i need to use p1,p2,p3,...pn in another equation. so i dont know to to save this elements from A. how to use loop to that it automatically get saved for n elements

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Answer 1

Matt J 2021-9-15

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It is not a good idea to store A(i) in separate variables. You should probably just write your equation in terms of vector operations on A, which you already have.

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gourav pandey 2021-9-15

Hii Matt, thank you

i fully agree with you. actually, i am a beginner, so no idea how to use.

if my function is in this way

fun= p1*r^2+p2*ln(r)+p3*cos(theta)/r+p4*sin(theta)/r+(pn*r^(-n+2))*cos(n*theta)

then how to do that?

Matt J 2021-9-15

在 MATLAB Online 中打开

A(1)*r^2+A(2)*ln(r)+A(3)*cos(theta)/r+A(4)*sin(theta)/r+(A(n)*r^(-n+2))*cos(n*theta)

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Answer 2

Awais Saeed 2021-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/1453499-how-to-develope-loop-to-save-the-n-elements-from-the-vectors#answer_787699

在 MATLAB Online 中打开

Although it is not prefered to name variables in a loop but if you striclty want to do this in loops than you can use eval(). Note that using this method is NOT RECOMMENDED. It has been said many times in this forum and by MATLAB itself.

https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

clc;
clear;
A= [14,51,2,15,7]
A = 1×5
    14    51     2    15     7
for col = 1:1:size(A,2)
	eval(['p',num2str(col),'=A(',num2str(col),')'])
end
p1 = 14
p2 = 51
p3 = 2
p4 = 15
p5 = 7