How can I plot a for loop?

Question

Mike Holbach 2015-3-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/181198-how-can-i-plot-a-for-loop

回答： Star Strider 2015-3-3

采纳的回答： Star Strider

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Can someone tell me what's wrong with this code? It is only plotting at x=6 because the loop obviously ends there.

e=2.718;

for x=-2:1:6

    if x<-1
        y=e.^(x+1)
    elseif x>=-1 && x<5
        y=2+cos(pi.*x)
    elseif x>=5
        y=10.*(x-5)+1
    else
        fprintf('answer not given')
    end
end
x=-2:6;
plot(x,y)

Thanks you

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Answer 1

Star Strider 2015-3-3

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/181198-how-can-i-plot-a-for-loop#answer_169904

在 MATLAB Online 中打开

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)