What does x(1,:) do in MATLAB ?

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JIIT Bainwala
JIIT Bainwala 2012-5-11
评论： Steven Lord 2024-6-10
What does x(1,:) do in MATLAB ?
eg:
at = sqrt(Po)*exp(-0.5*(1+i*C)*(tau./t0).^(2*m))
a0 = fft(at(1,:));
what does at(1,:) do here ?
  2 个评论
Anil Chowdary Tummala
Anil Chowdary Tummala 2021-4-21
Q1. What does x(1,:) do in MATLAB ?
Answer : It gives the first row of matrix 'x'
Q2. what does at(1,:) do here ?
Answer : it gives the first row of FFT coefficients of matrix 'at'

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采纳的回答

Dr. Seis
Dr. Seis 2012-5-11
"a0" is the Fourier Transform of the first row of "at"
at(2,:) % gives the second row
at(3,:) % gives the third row (and so on)
at(:,1) % gives the first column (and so on)

更多回答（3 个）

Afissou ZONGO
Afissou ZONGO 2021-8-17
X(i*2,:) means
  1 个评论
Walter Roberson
Walter Roberson 2021-8-17

Take the current value of the variable i and multiply it by 2. Use the result as row indices to select entire rows of X.

The code shown does not require that i is a scalar or even a vector. It also does not require that the values in i are currently integer values, but if they are not then there is the risk that there could be an indexing error.

There are uncommon cases in which i would not necessarily have to be numeric, but you might never see that happen in practice.

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Sorabh Mahajan
Sorabh Mahajan 2022-2-27
x = [x;i] meaining
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Walter Roberson
Walter Roberson 2022-2-28
[A;B] is defined as being vertcat(A, B) which in turn is defined as being the same as cat(2,A,B)
That is, [x;i] takes the existing array x, and tries to place a new row containing i at the bottom of it. With the x= assignment that becomes the new x. The effect is to add the content of i to the bottom of x.

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Antonio
Antonio 2024-6-10
x(1:2,1)? meaning
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Steven Lord
Steven Lord 2024-6-10
This performs "Indexing with Element Positions". In particular, "You can also reference multiple elements at a time by specifying their indices in a vector."

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