# How to normalize two waves on a single plot

56 views (last 30 days)
Lakerpurp24 on 11 Sep 2019
Commented: Star Strider on 11 Sep 2019
Basically i want to normalize and display the maximum and minimum values between y and y2 for the following code so that they both display on the same plot
t=0:0.001:0.05;
y= 11.18*cos(60*pi*t+26.565);
y2= -60*pi*11.18*sin(60*pi*t+26.565);
title('Phasor Waveforms')
f1=max(y);
f2=max(y2);
hold on
plot(t,y)
plot(t,y2)
hold off

Star Strider on 11 Sep 2019
Try this:
t=0:0.001:0.05;
y= 11.18*cos(60*pi*t+26.565);
y2= -60*pi*11.18*sin(60*pi*t+26.565);
title('Phasor Waveforms')
f1=max(y);
f2=max(y2);
figure
yyaxis left
plot(t,y)
yyaxis right
plot(t,y2)
See the documentation for yyaxis (R2016a and later releases, earlier releases plotyy, and different code) for details.

Lakerpurp24 on 11 Sep 2019
this worked! thanks! but now i have a new error. trying to plot the max using this code:
idymax = find(y == max(y));
plot(t,y,'o',[idymax],'MarkerFaceColor','red','MarkerSize',15)
produced this error:
Error using plot
There is no o property on the Line class.
im using version 2019a, thank you so much for your time!
Star Strider on 11 Sep 2019
As always, my pleasure!
I’m not sure what you want to do.
Try this:
t=0:0.001:0.05;
y= 11.18*cos(60*pi*t+26.565);
y2= -60*pi*11.18*sin(60*pi*t+26.565);
title('Phasor Waveforms')
f1=max(y);
f2=max(y2);
idymax = find(y == max(y));
figure
yyaxis left
plot(t,y)
hold on
plot(t(idymax),y(idymax),'o','MarkerFaceColor','red','MarkerSize',15)
hold off
yyaxis right
plot(t,y2)
If you want to plot a point or a series of values, the subscripts for those values need to be the same for all coordinates.
The find function will return the indices of all the values that are equal to ‘max(y)’ here. If there is only one ‘y’ maximum, an alternative could be:
[f1,idymax]=max(y);
since the max function will return the index to the first maximum it discovers.
Star Strider on 11 Sep 2019
If you assign that logical operation to a variable it returns a logical vector of false (0) values, except for the maximum (true,1) to the variable:
q = y == max(y)
Otherwise, without the assignment, it does not appear to do the logical operation. (I did that experiment.)

KSSV on 11 Sep 2019
t=0:0.001:0.05;
y= 11.18*cos(60*pi*t+26.565);
y2= -60*pi*11.18*sin(60*pi*t+26.565);
title('Phasor Waveforms')
y=y/max(y) ;
y2=y2/max(y2) ;
[f1,idx1]=max(y);
[f2,idx2]=max(y2);
hold on
plot(t,y)
plot(t,y2)
plot(t(idx1),f1,'*r')
plot(t(idx2),f2,'*b')
hold off