How to plot a graph with negative and small value of X ..help..thx

This is my code...the result i want is a graph with negative values of X from -0.0025 to 0.0025...however, the result from the following is different with positve and large values of x..pls help me to change the code a bit..thxxx

tt = -0.00025:0.00001:0.00025
x1 = 20*cos(2*pi*(4000)*(tt -37.2/10));

tt = -0.00025:0.00001:0.00025
x2 = 24*cos(2*pi*(4000)*(tt +41.3/10));

x3= x1+x2

subplot(3,1,1),plot(x1)
title('X1')

xlabel('Time(sec)')

subplot(3,1,2),plot(x2)
title('X2')
xlabel('Time(sec)')

subplot(3,1,3),plot(x3)
title('X3')

xlabel('Time(sec)')

Answer 1

[Star Strider]

You need to plot both the x and y vectors in your plot statements.

This works:

tt = -0.00025:0.00001:0.00025;
x1 = 20*cos(2*pi*(4000)*(tt -37.2/10));

tt = -0.00025:0.00001:0.00025;
x2 = 24*cos(2*pi*(4000)*(tt +41.3/10));

x3= x1+x2;

subplot(3,1,1)
plot(tt,x1)
title('X1')
xlabel('Time(sec)')
axis([min(tt) max(tt)    ylim])

subplot(3,1,2)
plot(tt,x2)
title('X2')
xlabel('Time(sec)')
axis([min(tt) max(tt)    ylim])

subplot(3,1,3)
plot(tt,x3)
title('X3')
xlabel('Time(sec)')
axis([min(tt) max(tt)    ylim])

The axis function limits the axes to what you specify. If you want them to go from [-3,3] instead, simply remove the axis calls.

Answer 2

[elaine]

Thank you sooo much...it's my first time using Matlab...^^

[Star Strider]

My pleasure!

MATLAB has a lot of online resources that will make it much easier for you to become proficient. If you have problems getting your code to run, we’re here to help!