Fixing loop values while plotting

Asked by Fabiano Da Mota

Fabiano Da Mota (view profile)

on 23 Apr 2019
Latest activity Commented on by Fabiano Da Mota

Fabiano Da Mota (view profile)

on 24 Apr 2019
Hello All,
I have been practicing matlab for fun for sometime now and I am getting into plotting data structures at the moment. I have been trying to "fix" certain loop values while plotting but I have been having a hard time getting this to work. In the code below, I would like to plot all the 'b" values for y=1 and z=1 while x=1:3. I can easily do this by fixing one of the variables but I currently can not fix y and z at the same time. Please see my simple code below. Any advice would be greatly appreciated! Thank you!
vals.y=[];
vals.x=[];
vals.b=[];
vals.z=[];
for z = 1:3;
for y = 1:3;
for x=1:3;
b = x*y*z;
vals.y(end+1)=y;
vals.x(end+1)=x;
vals.b(end+1)=b;
vals.z(end+1)=z;
end
end
end
plot(vals.b(vals.y==1),vals.x(vals.y==1));
%plot(vals.b(vals.y==1 & vals.z==1,vals.x(vals.y==1 & vals.z==1)); - Would Like to this
% to this

Release

R2018b

Answer by Shunichi Kusano

Shunichi Kusano (view profile)

on 24 Apr 2019

Your code almost works. You need a closing parenthesis.
plot(vals.b(vals.y==1 & vals.z==1,vals.x(vals.y==1 & vals.z==1)) % your code
plot(vals.b(vals.y==1 & vals.z==1),vals.x(vals.y==1 & vals.z==1)) % corrected code
And one suggestion. It's a good practice that you do not use for-loop, if you can. In this case, The following code is prefarable. This is easier to write and faster to calculate.
[vals.x, vals.y, vals.z] = meshgrid(1:3);
b = vals.x .* vals.y .* vals.z;

Fabiano Da Mota

Fabiano Da Mota (view profile)

on 24 Apr 2019
Hello Shunichi,
Thank you very much! I have been trying different things for a couple of hours and the solution was simpler than I expected. Thank you again.