for loop storing the same variable

Question

Reinhardt RADING 2022-8-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1775760-for-loop-storing-the-same-variable

评论： Steven Lord 2022-8-8

采纳的回答： Matt J

I have a for loop as below:

I is intensity of length 1000 (constant)

noise is a random white noise of length 1000

demodulated_power_vector1=zeros(floor(length(I)/4),4);

demodulated_power_vector2=zeros(floor(length(I)/4),4);

demodulated_power_vector3=zeros(floor(length(I)/4),4);

demodulated_power_vector4=zeros(floor(length(I)/4),4);

for ii=0:floor(length(I)/4)

for ss= 0:floor(length(noise)/4)

demodulated_power_vector1(:,1)=(I(1+ii)/2)*(1+cos(Dphi+noise(1+ss)+pi-alphaa));

demodulated_power_vector2(:,2)=(I(2+ii)/2)*(1+cos(Dphi+noise(2+ss)+pi+alphaa));

demodulated_power_vector3(:,3)=(I(3+ii)/2)*(1+cos(Dphi+noise(3+ss)-pi+alphaa));

demodulated_power_vector4(:,4)=(I(4+ii)/2)*(1+cos(Dphi+noise(4+ss)-pi-alphaa));

end

Why is the for loop storing the same variable? I'm getting the same answer. for example, the 250 variables stored in demodulated_power_vector1 are the same.

I dont know what i'm doing wrong. Kindly assist.

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Answer 1

Matt J 2022-8-8

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1775760-for-loop-storing-the-same-variable#answer_1022830

编辑：Matt J 2022-8-8

在 MATLAB Online 中打开

Because in every pass through the loop, you assign the result to the same location. Perhaps you meant,

demodulated_power_vector1(ii,1)=(I(1+ii)/2)*(1+cos(Dphi+noise(1+ss)+pi-alphaa));

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Matt J 2022-8-8

See my suggestion above.

Steven Lord 2022-8-8

在 MATLAB Online 中打开

Since this assignment is inside two for loops @Reinhardt RADING probably wants to use both ii and ss to specify the "target" section of the demodulated power vector into which MATLAB should assign the output of the calculations to the right of the equals sign. But as a matter of fact, the suffixes (1, 2, 3, and 4) that distinguish the four demodulated power vectors probably also should be indices, making demodulated_power_vector a 3-dimensional array.

See this Answers post for some motivation behind moving the suffixes into actual indices.

demodulated_power_vectors = zeros(floor(length(I)/4),4, 4);

With appropriate calls to reshape it may be possible to eliminate one or both of the for loops.

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