Step function with a ramp. Error in the creation of the ramp

Question

Giorgos Papakonstantinou 2013-1-27

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I am trying to create a ramp which is a part of a step function in order to plot it.

 x=1e-6:1e-6:L;
  for i=1:10
      bl(i)=(2*i-1)*9.35e-4+(i-1)*8e-5;
      bu(i)=(2*i-1)*9.35e-4+i*8e-5;
      I(x>=bl(i) & x<bu(i))=(i-1)*1.26e-2+150.*(x-bl(i)); % Current in part b of the unit cell
  end

But I get this error:

In an assignment  A(I) = B, the number of elements in B and
I must be the same.

Do you know the solution?

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Azzi Abdelmalek 2013-1-27

What is the initial value of I. What is the expected value of I ?

Can you explain what do you want to achieve?

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Answer 1

Matt J 2013-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/60019-step-function-with-a-ramp-error-in-the-creation-of-the-ramp#answer_72567

在 MATLAB Online 中打开

idx=(x>=bl(i) & x<bu(i));
I(idx)=(i-1)*1.26e-2+150.*(x(idx)-bl(i));

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Giorgos Papakonstantinou 2013-1-28

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Matt I have followed the same procedure to create a plot based on the integral of the equation that I wrote above. The problem is that I have discontinuities in the limits of the intervals when I plot the integral of the equation. I haven't been able to fix until now. I am attaching you the code below. Perhaps you can see something that I cannot see.

clc
clear
jmpp=350; % [A/m^2]
Rb=0.01; % [Ω/sq]
L=0.0195;
Wf=1000e-6;
lf=L*0.481;
n=1;
D=L./(2*n);
S=D-Wf./2;
Wb=L-2.*lf;
x=1e-6:1e-6:L;
Iline=(4*jmpp*S*lf)/Wf; % line current
I=zeros;
P=zeros;
Pb=zeros;
Pi=zeros;
[al, au, bl, bu, cl, cu]=deal(zeros(1,n));
for i=1:n
    al(i)=2*(i-1)*S+(i-1)*Wf;
    au(i)=(2*i-1)*S+(i-1)*Wf;
    bl(i)=(2*i-1)*S+(i-1)*Wf;
    bu(i)=(2*i-1)*S+i*Wf;
    cl(i)=(2*i-1)*S+i*Wf;
    cu(i)=2*i*S+i*Wf;
    a=(x>=al(i) & x<au(i));
    b=(x>=bl(i) & x<bu(i));
    c=(x>=cl(i) & x<cu(i));
    t=(x>=al(i) & x<=cu(i));   
    I(a)=(i-1)*Iline*Wf; 
    P(a)=(Iline.^2.*Rb.*Wf.^2.*(x(a)-al(i)).*(i - 1).^2)./Wb;
    Psuma(i)=(Iline^2*Rb*S*Wf^2*(i - 1)^2)/Wb; 
    I(b)=(i-1)*Iline*Wf+Iline.*(x(b)-bl(i)); 
    P(b)=(Iline.^2.*Rb.*(x(b)-bl(i)).*(3.*Wf.^2 - 6.*Wf.^2.*i - 3.*Wf.*(x(b)-bl(i)) + (x(b)-bl(i)).^2 + 3.*Wf.^2.*i.^2 + 3.*Wf.*i.*(x(b)-bl(i))))./(3.*Wb)+Psuma(i);
    Psumb(i)=(Iline^2*Rb*Wf*(12*S^2*i^2 - 12*S^2*i + 3*S^2 + 24*S*Wf*i^2 - 30*S*Wf*i + 9*S*Wf + 12*Wf^2*i^2 - 18*Wf^2*i + 7*Wf^2))/(3*Wb); 
    I(c)=i*Iline*Wf; 
    P(c)=(Iline.^2.*Rb.*Wf.^2.*i.^2.*(x(c)-cl(i)))./Wb+Psumb(i);
    Psumc(i)=(Iline^2*Rb*S*Wf^2*i^2)/Wb; 
    I(x>=cu(i))=i*Iline*Wf;
    P(x>=cu(i))=Psumc(i);
end
figure(1)
plot(x*1e2,I)
figure(2)
plot(x*1e2,P)

Thank you once again!

Matt J 2013-1-28

在 MATLAB Online 中打开

Here's a somewhat lazy way of doing it,

 t=linspace(0,12,1e4);
 f=@(x) 5.*(x<=5) +x.*(x>5 & x<=10) + 10*(x>10);
 plot(t,f(t)); ylim([4,11])

Giorgos Papakonstantinou 2013-1-29

Thank you Matt

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Answer 2

Image Analyst 2013-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/60019-step-function-with-a-ramp-error-in-the-creation-of-the-ramp#answer_72568

编辑：Image Analyst 2013-1-27

在 MATLAB Online 中打开

Have you considered linspace() instead?

    bl = linspace(9.35e-4, 19*9.35e-4+9*8e-5, 10)  
    bu = linspace(9.35e-4, 19*9.35e-4+10*8e-5, 10)
    output = linspace(0, 9*1.26e-2, 10)+150*(x-bl)
    indexesToSet = x>=bl & x<bu % Only set those elements satisfying this.
    I(indexesToSet) = output(indexesToSet)

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Answer 3

Giorgos Papakonstantinou 2013-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/60019-step-function-with-a-ramp-error-in-the-creation-of-the-ramp#answer_72572

编辑：Giorgos Papakonstantinou 2013-1-27

I didn't know about linspace. I would definitely try it out. Thank you both!

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Image Analyst 2013-1-27

It's just a more MATLAB-ish way of doing things since it avoids a loop, though with only 10 iterations, looping is definitely not a bottleneck. If you had tens of millions of iterations, it might make a noticeable effect.

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Step function with a ramp. Error in the creation of the ramp

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