I need help preallocating array?
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I need help making this array preallocated.
p = 10;
newArray = [];
array = [];
for i = 1:p
a= variable1;
b = variable2;
c = variable3;
d = variable4;
e = variable5;
array = [a,b,c,d,e]
newArray= [newArray array];
end
采纳的回答
pfb
2015-4-12
Look at the function "zeros".
array = zeros(1,5);
newArray = zeros(1,5*p);
and, in the loop
newArray((1+(i-1)*5):(i*5))=array;
This way all you need is allocated before the loop.
I assume that the assignments of a through e come from function that have a different value for different i's.
If they are the same, it's just a tiling problem. You need "repmat".
5 个评论
ME
2015-4-12
pfb
2015-4-12
well, it's simply what you want to do, I guess.
At the ith iteration you put the content of "array" into the elements of newArray going from 1+(i-1)*5 to (i*5).
That is:
- when i = 1 the elements go from 1 to 5 - when i = 2 the elements go from 6 to 10 - and so on
This avoids concatenating array at the end of newArray, which in general slows you down.
But now you talk of rows.. What exactly do you want to attain here? Should newArray be a very long row vector or a p by 5 matrix?
ME
2015-4-12
ME
2015-4-12
not really in a new row.
In your code "array" is copied at the end of the row vector newArray. No new rows.
Use the semicolon operator to add new rows. You should have written
myArray = [myArray; array];
I think you should read some documentation.
Anyway, to allocate your matrix (not vector)
newArray = zeros(p,5);
Filling it, now is much simpler. This fills the ith row of newArray with the current values in array.
newArray(i,:) = array;
You should state your problem better. Apparently, what you needed was filling the rows of a matrix, all the time.
And perhaps take a look into the basics of matlab.
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