Having the following code in Matlab:
r= zeros(10,10);
r(:) = x(z);
given that "x" is a single dimension array and "z" is a 2d array what is the function
r(:) = x(z); doing and how could I implement something similar in Java?
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what do you need? an array containing a 2d array? Please be clearer and you will get your answer quickly. :)Pat B– Pat B2011-12-06 15:53:52 +00:00Commented Dec 6, 2011 at 15:53
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well first I would need somebody to explain what x(z); does as I found some code in Matlab and want to implement it in Java but I don't know what it is exactly doing.Radek– Radek2011-12-06 15:58:24 +00:00Commented Dec 6, 2011 at 15:58
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2 Answers
Firstly, x(z) takes each element in the 2d-array z, and uses it as an index to fetch data from x.
For example x=[1 2] z = [1 1; 1 2] would give the result x(z) = [1 1; 1 2] because x(z) is really [x(z(1,1)) x(z(1,2)); x(z(2,1)) x(z(2,2))]. Therefore you have to be careful that the values in z doesn't exceed the size of x or you'll get index out of bounds.
r(:) = x(z) is basically the same as r = x(z).
To implement this in java you would need som kind of for-loop over the elements in z. In this loop you would construct a 2d-array by assigning the current index (i,j) with the value in x(z(i,j)).
Hope this helps!
Comments
So the java code looks as follows:
for (int i = 0; i < z.length; i++) {
for (int j = 0; j < z[0].length; j++) {
y[i][j] = x[z[i][j]];
}
}