How to write a for loop that saves every 100th value?

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Lauren Miller
Lauren Miller 2021-4-30
编辑： Scott MacKenzie 2021-4-30
I have a code that has a for loop that calculates the eccentricity of an orbit as time passes, and I need to plot the results. Saving every single value of accentricity would be very large task, so I need to save every 100th value of eccentricity, along with the corresponding time, to some type of file.
This is what I have so far but it very much doesn't work, any advce would be greatly appreciated.
m = 0;
for i = 1: m
m = m + 1;
if m == 100
C{i} = emag;
C2{i} = t;
E(i,1) = emag;
E(i,2) = t;
matrixToWrite = [t emag];
writematrix(matrixToWrite, 'myData.txt')
m = 0;
t = t + delta;
end
end
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Rik
Rik 2021-4-30
In general you can do that by editing the question instead of posting a new one.

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采纳的回答

Scott MacKenzie
Scott MacKenzie 2021-4-30
编辑：Scott MacKenzie 2021-4-30
If I understand your quesiton correctly, a for-loop is not necessary. It seems you have an array emag with many values and a corresponding array t with the timestamp for each value. Here's some code (using mock arrays) that saves every 100th value in t and emag in a file mydata.txt:
emag = rand(1,23456);
t = rand(1,23456);
n = length(emag);
emag100 = emag(1:100:n);
t100 = t(1:100:n);
writematrix([emag100' t100'], 'mydata.txt');

更多回答（1 个）

EmirBeg
EmirBeg 2021-4-30
First of all you set m=0 and then start a loop from 1 to m. So i guess your loop does nothing.
You need to set a new variable for the amount of iterations your loop will go through. After that you should also set m to 0 again in your If-statement so you get a value every 100th iteration and not just the 100th.
  2 个评论
EmirBeg
EmirBeg 2021-4-30
I realise that you already added the m=0 in your If-statement or i was blind and didn't see it.
This should still be changed:
m = 0;
t = 5000; %amount of times you go through the loop
for i = 1: t
m = m + 1;
if m == 100
%...
end
end

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