plotting mat file with different sampling frequencies.. COMMENTS PLEASE

I'm given this g(t) sound signal. I'm supposed to sample this signal with sampling frequencies 8KHz and 4KHz, then plot these two sampled signals. I tried until doing the sampling part, but don't know how to plot it..I googled this but got no useful information. The g(t) signal is given as g1.mat and it's a 48000*1 double struct.

%%Sampling
x1 = load('g1.mat');
f = fieldnames(x1);
sound(x1.(f{1}),8000);

I got until here but can't proceed..Can anyone help me plot the g(t) signal sampled at 8KHz, 4Khz on the frequency domain? By the way, if i change sound(x1.(f{1}),8000); this part to 4000, the duration of the sound is different. I was asked to make the duration same. How can i modify this too?

Thanks

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Walter Roberson]

t = (0:length(x1.f1)-1)/8000;
plot(t, x1.f1)

To make the duration the same, you need to resample. There are several ways to do that. Perhaps some particular resampling techniques have been discussed in class?