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

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Robin Oldfield 2021-1-20

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评论： Robin Oldfield 2021-1-22

I am trying to calculate all values of velocity and displacement for the times between 0 and 20 in increments of 0.01. Im struggling to add on the last value of velocity and displacement as i need to be able to use the previous iteration values where i have tried doing this using the variable 'i'. I think the problem is due to the different sizes of matrices. Im quite new to coding so any help would be appreciated, thanks.

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Katie 2021-1-20

Can you please attach or copy your code so we can see how you're setting it up? Thanks!

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Answer 1

Walter Roberson 2021-1-20

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在 MATLAB Online 中打开

dt = 0.01;
i0 = 1;
i(1) = i0;
i = (1:dt:21);

Note that overwrites all of i

It is not recommended to use i as a variable name, as it can lead to confusion because i is used as sqrt(-1)

i will be a vector of length 2001 I think.

for t = [0:0.01:20.0]
   v(i+1) = a*0.01 + a(i)*t;

You ask to index a(i) but a appears to be a scalar at that point, and i contains non-integer values that are not valid as indices.

You also multiply all of a by 0.01 so if a is a non-scalar (due to code you did not show us) then it might not be the same size as a(i) .

If somehow (that is, if the code you posted is not the code that generated the error) i were a scalar integer at that point but a were a vector, then v(i+1) would hypothetically designate a scalar, but a*0.01 would be a vector and you would be trying to store a vector result into a scalar field.

... But the code you posted would have failed before that, failing when trying to index a at the non-integer i