How to run multiple for loops for values of x up to y and then from y up to z.

Hello!

I am trying to write a script that will plot a graph of x against y.

My values of x go from 0 to b in 1000 steps.

I also have another value 'i' which is used in the initial for loop.

a and c are just two values inputted earlier in the script.

So to start with I have:

 x = linspace(0,b,1000);
 for i = imin : iinc : imax
      for x < a
          y = some function
      end

      for a < x < c
          y = some function
      end
end

I know that the two internal for loops wont run but im not sure how to write it so that they do.

Any help would be appreciated, Thanks!

[Mark Smith]

Could it look something like this?

 x = linspace(0,b,1000);
 for i = imin : iinc : imax
      for p = x : a
          y = some function
      end
      for q = x : c
          y = some function
      end
end

[Guillaume]

for p = x : a

when x is an array is the same as

for p = x(1) : a

Not at all what the OP is asking.

Answer 1

[Guillaume]

a = 3; b = 30; c = 4; %for example
x = linspace(0,b,1000);
%ignoring the i loop, since it's irrelevant to your question
for xx = x(x < a)
  %do something with xx
  fprintf('in 1st loop, xx = %f\n', xx);
end
fprintf('\n');
for xx = x(x > a & x < c)
  %do something with xx
  fprintf('in 2nd loop, xx = %f\n', xx);  
end

Answer 2

[Thorsten]

You don't need loops. Use logical indices instead:

b = 10; x = linspace(0,b,1000);
ind = x < a;
y(ind) = x(ind).^2; % some function on x
c = 8;
ind = (a <= x) & (x < c);
y(ind) = x(ind).^3; % another function on x
plot(x,y)

[Guillaume]

"You don't need loops". Well, that depends on the unspecified function. It may only work on scalars.