How can one define this vector in an elegant way?

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alpedhuez
alpedhuez 2020-6-2
评论： Walter Roberson 2020-6-18
I have
x=0:0.01:1
then I want to create a vector y that corresponds to each value of x
ngrid=((1-0)/0.01)1;
y=zeros(ngrid,1);
What will be a compact way to define y?
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Suraj Sudheer Menon
Suraj Sudheer Menon 2020-6-14
An approach could be to perform elementwise multiplication and perform transpose operation to obtain the a column vector.
y=(x.*0)' ;

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Steven Lord
Steven Lord 2020-6-18
As Walter Roberson said in a comment if you want to preallocate y to be the same size as x, you can do that using functions like zeros, ones, nan, inf, etc.
x = 0:0.1:1;
y = zeros(size(x))
But depending on what calculations you're performing to "calculate the value of y for each grid point of x" you may be able to just do those calculations. For instance, the .^ operator is an element-wise operator that can operate on an array of data.
x = 0:0.1:1;
z = x.^2; % Raise each element of x to the second power, no preallocation required
% Show the results
plot(x, z)
I have one other general comment. I've noticed you've been asking a lot of pretty basic questions about MATLAB, so I suspect you're new to using it. Is that correct? If so you may want to work through the MATLAB Onramp tutorial. It teaches the basic foundations of MATLAB and so may give you solid footing as you learn more about MATLAB and start writing more complicated MATLAB code.

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Suraj Sudheer Menon
An approach could be to perform elementwise multiplication and perform transpose operation to obtain the a column vector.If a row vector of the same characteristics are needed the transpose operation can be avoided.
y=(x.*0)' ; (column vector);
y=(x.*0) ; (row vector)
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Walter Roberson
Walter Roberson 2020-6-18
.* is element-by-element multiplication. x.*0 is an all-zero array the same size as x. (x.*0)' is the conjugate transpose of that all-zero array, and since 0 is real, that is the same as the plain transpose of the all-zero array. When x is a row vector, the all-zero array would be a row vector and the transpose of it would be a column vector of zeros with the same number of elements as x had.

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