how to plot complex functions of phase and amplitude

I am trying to use f(t)=(1+0.25i)t–2.0 to plot the amplitude and phase of function f for 0 less than or equal to t less than or equal to 4 on two separate subplots within a single figure.

[SP]

can you help me again;

I am trying to create an array of 100 input samples in the range of 1 to 100 using the linspace function, and plot the equation y(x)=20 log10(2x) on a semilogx plot. I would also like to draw a solid blue line of width 2, and label each point with a red circle. And I want to create an array of 100 input samples in the range of 1 to 100 using the logspace function, and plot the equation y(x)=20 log10(2x) on a semilogx plot with a solid red line of width 2, and label each point with a black star.

[SP]

hi I would greatly appreciate your help again I am kind of stuck,

I am trying to create the spiral of archimedes by the equation r = θ and r is the distance of a point from the origin and θ is the angle of that point in radians. I am trying to plot the spiral of archimedes for 0 less than or equal to θ less than or equal to 6pi when k =0.5 so far I have this:

>> theta=0:pi/6:6*pi;

>> k=0.5;

>> r=k*theta;

>> polarplot(theta,r)

However I am not getting a regular spiral

Answer 1

[Star Strider]

Try this:

f = @(t) (1+0.25i).*t-2.0;
t = linspace(0, 4);

figure
subplot(2,1,1)
plot(t, abs(f(t)))
title('Amplitude')
subplot(2,1,2)
plot(t, angle(f(t)))
title('Phase')

[Star Strider]

In for a d, in for a £:

x1 = logspace(0,2);
y1=20*log10(2*x1);

figure(1)
semilogx(x1,y1,'-b','LineWidth',2)
hold on
plot(x1, y1, 'or')
hold off
title('Plot title');
xlabel('X Axis')
ylabel('Y Axis')

figure(2)
semilogx(x1,y1,'-r','LineWidth',2)
hold on
plot(x1, y1, 'pk')
hold off
title('Plot title');
xlabel('X Axis')
ylabel('Y Axis')

[Brewsky]

you sir, are a god amongst men. thank you for your service!

[Star Strider]

@Brewsky —

My pleasure!

I very much appreciate your compliment!

[James Calandro]

Thank you so much! This was exactly what I needed.

[Star Strider]

James Calandro — My pleasure!

(A Vote would be appreciated!)