plot square with a given average value

Hi all,

I want to ask a question about plotting a square waveform by using Matlab. I can plot the square waveform with square() function but i don't know how i can draw a square wave with a certain average value. i must plot a square waveform with an average value -2.

Best regards, Dilem

Answer 1

[Wayne King]

     t = 0:.0001:.0625;
     y = square(2*pi*30*t)-2;
     plot(t,y); set(gca,'ylim',[-3.5 -0.5]);
     hold on; grid on;
     plot(t,mean(y).*ones(length(y),1),'r');

If you want it exactly -2,

      y = square(2*pi*30*t);
      y = y-mean(y)-2; 
      plot(t,y); set(gca,'ylim',[-3.5 -0.5]);
      hold on; grid on;
      plot(t,mean(y).*ones(length(y),1),'r');

[dilem]

Isn't average value equal to the area that is underneath positive one period of square wave? if so how can an area be negative? how can I calculate -2 as average value from your solution?

[Wayne King]

no, look at the mean-value theorem for integrals if you want to think of the square wave as a continuous time function. If you want to think of it as a vector, you simply sum the elements of the vector and divide by the number of elements.

y = square(2*pi*30*t);

y = y-mean(y)-2;

mean(y)

you get -2. The mean of y is -2. You can also see from the plot that I showed you how to produce that the mean value is -2.

[dilem]

thank you for your attention and time.