DTMF (Dial Tone) Help

The question asks:

Read the “dtmf.wav” audio file using audioread function of MATLAB Identify the corresponding 4-digit dialed number

Show all your work and plot the DFT’s of all the digits

Please use a DFT of size 2048 to estimate the digital digits.

Here is the frequency table:

Here is my code:

y = audioread("dtmf.wav");
z = plot(y) % which gives me the the plot of the four digits but I need to decode it to find the frequency range and with that I can find the four digit numbers

N = 2048;
fs = 44100;
T = 1/fs;
t = T*(0:N-1);

I'm having trouble sampling z = plot(y). Right now it's in time domain, but I need it to be in the frequency domain. Please help! I need to output the plot for all 4 digits.

[Walter Roberson]

The first example of the documentation for fft() shows how to plot in the frequency domain

[Jonathan Diaz]

Which is? I don't understand..

[Walter Roberson]

https://www.mathworks.com/help/matlab/ref/fft.html#buuutyt-7

First it plots in the time domain. Then in the lines starting from "Compute the Fourier transform of the signal. " it shows calculation of the fft and shows plotting in the frequency domain.