MATLAB: I put the code in, but when the grapg shows there is nothing… I don’t know what im going wrong and it NEEDS to be a for loop

for loopplotting

for x=0:360
y= cosd(x)
end
plot(x,y)

Best Answer

You need to tweak your code just a bit:

x=0:360;
for k1 = 1:length(x)
    y(k1) = cosd(x(k1));
end
plot(x,y)

You have to address every element of ‘x’ separately in each iteration of the loop, and store every value calculated in vector ‘y’. Use the same value of the index variable in each vector.

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MATLAB: Help with Alogrithm???

You could save the x and y result from each iteration in a vector, but rather that do that you don't really need the for loop at all. E.g.,

s=pi/180; %to make radians.
i=1:360; %for every degree
t=s*i;          %degree in to radians
x=30*cos(t);
y=15*sin(t);
plot(x,y)

MATLAB: How to plot a for loop

You’re not subscripting either ‘x’ or ‘y’. That’s important because ‘x’ is negative and zero, so it can’t be used as indices. Also, the lengths of both vectors have to be the same.

A few tweaks and your code works:

e=2.718;
x=-2:1:6;
for k1 = 1:length(x)
      if x(k1)<-1
          y(k1)=e.^(x(k1)+1);
      elseif x(k1)>=-1 && x(k1)<5
          y(k1)=2+cos(pi.*x(k1));
      elseif x>=5
          y(k1)=10.*(x(k1)-5)+1;
      else
          fprintf('\nanswer not given\n')
          y(k1) = NaN;
      end
  end
  x=-2:6;
  plot(x,y)

Best Answer

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MATLAB: Help with Alogrithm???

MATLAB: How to plot a for loop

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