simple multiplication / summation using matlab
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i want to do some complicate calculations by matlab of following
n=0:65119;
x = cos(3.6*n)*sin(3.6*n);
y = x*x
it shows errors however, saying
Error in ==> ex3_1_2 at 3 x = cos(3.6*n)*sin(3.6*n);
what's happening?
采纳的回答
Walter Roberson
2012-10-4
The MATLAB operator "*" is matrix multiplication. Element-by-element multiplication is ".*"
cos(3.6*n) .* sin(3.6*n)
5 个评论
Passband Modulation
2012-10-4
Passband Modulation
2012-10-4
sry to bother u again. now the modified code becomes
n=0:65119;
x = cos(3.6.*n).*sin(3.6.*n);
y = x.*x
the result turns out to a series of numbers? so strange as mathematically it should have been a single number??
matlab result:
Jan
2012-10-4
"n" is a vector, "cos(3.6 * n)" is a vector , "cos(3.6 * n) .* sin(3.6 * n)" is a vector, then "x .* x" is a vector also. Why do you expect a scalar? Do you want:
y = x * transpose(x)
Passband Modulation
2012-10-4
Walter Roberson
2012-10-4
You did not happen to show us the mathematical notation for what you are trying to do.
In MATLAB, 0:65119 is a row vector, 1 x 65120 in length. Matrix multiplication of two row vectors cannot be done: Matrix multiplication (mathematically) requires that the "inner dimensions" must be equal. Matrix multiplication is defined for (1 x 65120) * (65120 x 1) (giving a 1 x 1 result), and is defined for (65120 x 1) * (1 x 65120) (giving a 65120 x 65120 result), but it is not defined for (1 x 65120) * (1 x 65120)
It is mathematically possible to dot-product or cross-product vectors that have the same orientation; we cannot tell whether that is your intention.
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2012-10-4
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