How can I concatenate arrays in loop ?

2 次查看（过去 30 天）

显示更早的评论

Ender Rencuzogullari 2015-12-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/261373-how-can-i-concatenate-arrays-in-loop

评论： Ender Rencuzogullari 2015-12-22

采纳的回答： Guillaume

在 MATLAB Online 中打开

Dear Contributers,

There is a loop;

for i = 1:n;
X_rotate  = X.*cos(i*increment) - Y.*sin(i*increment);
Y_rotate  = X.*sin(i*increment) + Y.*cos(i*increment);
Helix  = [X_rotate(1:K1) ; Y_rotate(1:K1)];
fileID = fopen('helix_values.txt', 'w');
fprintf(fileID,'%f %f\n ', Helix);
fclose(fileID);
end

When open the text file, there just exists the last values of iteration X_rotate and Y_rotate. I need to collect the values for every iteration. I have tried to use cat command but I probably made mistake. How may I do that?

Thanks in advance.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Guillaume 2015-12-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/261373-how-can-i-concatenate-arrays-in-loop#answer_204043

在 MATLAB Online 中打开

It looks like your X and Y are row vectors of size [1, K1] (inferred from the line Helix = [X_rotate(1:K1) ; Y_rotate(1:K1)];). In that case you don't need to use a loop to calculate your X_rotate and Y_rotate:

steps = 1:n;
X_rotate = bsxfun(@times, X, cos(steps*increment)') - bsxfun(@times, Y, sin(steps*increments)');
Y_rotate = bsxfun(@times, X, sin(steps*increment)') + bsxfun(@times, Y, cos(steps*increments)');
%rows of X_rotate and Y_rotate correspond to steps
%columns correspond to the original X and Y values

I'm unclear how you want to save all the iterations onto the same text file though, columns of X and Y multiplied by the number of iterations?

8 个评论
显示 6更早的评论隐藏 6更早的评论

Ender Rencuzogullari 2015-12-22

编辑：Ender Rencuzogullari 2015-12-22

My bad. I was trying to say that I want to collect the values of X_rotate and Y_rotate from their first value to K1 th value. not all of them

Ender Rencuzogullari 2015-12-22

Alright, I appreciate for your help :)

请先登录，再进行评论。

更多回答（1 个）

Star Strider 2015-12-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/261373-how-can-i-concatenate-arrays-in-loop#answer_204041

在 MATLAB Online 中打开

I’m not certain what you’re doing, but to get the ‘X_rotate’ and ‘Y_rotate’ as vectors, you have to save them as such:

for i = 1:n;
    X_rotate(i)  = X.*cos(i*increment) - Y.*sin(i*increment);
    Y_rotate(i)  = X.*sin(i*increment) + Y.*cos(i*increment);
end

I don’t know what their actual dimensions are, so you might have to add a second dimension to each:

for i = 1:n;
    X_rotate(i,:)  = X.*cos(i*increment) - Y.*sin(i*increment);
    Y_rotate(i,:)  = X.*sin(i*increment) + Y.*cos(i*increment);
end

Do the file write after the loop, not in it.

5 个评论
显示 3更早的评论隐藏 3更早的评论

Star Strider 2015-12-22

I am not certain how your program is organised. However a while loop with a counter, or some other way to determine the size of the user’s inputs, for example asking the user, would be useful to define ‘n’.

Ender Rencuzogullari 2015-12-22