How can I nest two loops of different dimension without using a for loop?
显示 更早的评论
Hi,
As the title says, I'm trying to nest two loops without using for loops, since they really delay the computation time.
For example:
I want n to vary from 1 to 365 (for each day of the year). Within that loop, I want h to vary from 11 to -12 (24 values for 24 hours) for each day.
n=1:365
delta=sind(360.*n)
h=11:-1:-12
i=1:length(h); %For indexing, because I can't index negative values
theta=cosd(delta).*sind(15.*h)
a=cosd(theta)
b=cosd(phi)./2
c=cosd(phi)./2
z(i)=a+b+c
%Increase n, repeat loop and add result to z each time
%Plot sum of loop return
figure(1)
plot(z)
I hope I was clear with my question. I would like the calculations done for one hour, put into z, done for the second hour, added to z, etc etc for the whole day (24 hours). Then, once the day completed, I want n to increase and redo the 24 hours. I want n to finish after 365 days.
I appreciate your time and input.
2 个评论
thebasher
2014-1-31
采纳的回答
phi = 0.1; % Undefined
n = 1:365;
delta = sind(360*n);
h = 11:-1:-12;
a= cos(bsxfun(@times,cosd(delta),sind(15*h)'));
b=cosd(phi)./2;
c=cosd(phi)./2;
z = a+b+c; % in z: 24 x 365 matrix
5 个评论
thebasher
2014-1-31
Amit
2014-1-31
no. You do not need loops.
The code I wrote here, calculates within that code for all 365 days and 24 hours.
bsxfun is a element-by-element operation. More details can be found at: http://www.mathworks.com/help/matlab/ref/bsxfun.html
I do understand that bsxfun can be confusing. Another approach instead of bsxfun is using repmat, which is simply repeating the vector given number of times. Using repmat, the line a will change like this:
a= cos(repmat(cosd(delta),24,1).*repmat(sind(15*h)',1,365));
thebasher
2014-1-31
Amit
2014-1-31
That is correct.
Z has 24 rows and 365 columns. Lets pick column 1 in z, then rows 1 to 24 in column represents values for z corresponding to n = 1 and h from 11 to -12 (all 24 values)
thebasher
2014-1-31
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息
Translated by 
