Calculate Matrix and then use previously calculated matrix in next iteration

Question

Alfie Mackie 2021-2-27

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/757864-calculate-matrix-and-then-use-previously-calculated-matrix-in-next-iteration

编辑： Jan 2021-2-27

I start with a set of values (1x50) and perform an equation. I then want the calculated values to be used in the next iteration of the equation instead of the original values, but I'm getting errors.

This is the code I have tried:

topog = 100:149;
erodedSed = (0.1:0.1:5);
newTopog = topog - erodedSed;
for i = 2:10;
    newTopog(i) = newTopog(i-1) - erodedSed;
end;

But I'm getting error:

"Unable to perform assignment because the left and right sides have a different number of elements.

Error in Untitled2 (line 6)

newTopog(i) = newTopog(i-1) - erodedSed"

Basically, instead of using "topog" in every iteration following the first, I want the code to replace topog with the "newTopog" calculated in the iteration before it, and then continue doing the equation for the further steps.

Many thanks for your help!

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Answer 1

Hernia Baby 2021-2-27

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/757864-calculate-matrix-and-then-use-previously-calculated-matrix-in-next-iteration#answer_634869

编辑：Hernia Baby 2021-2-27

在 MATLAB Online 中打开

" i " is not the number but index number(line or row).

e.g.1 using for

clear;
topog = 100:149;
erodedSed = (0.1:0.1:5);
newTopog(1,:) = topog - erodedSed;
for i = 2:10
    newTopog(i,:) = newTopog(i-1,:) - erodedSed;
end
newTopog(end,:)

e.g.2 using while instead of for (Recommended)

clear;
topog = 100:149;
erodedSed = (0.1:0.1:5);
newTopog = topog - erodedSed;
cnt = 1;
while cnt < 10
    newTopog = newTopog - erodedSed;
    cnt = cnt + 1;
end
newTopog