How do I add zero padding to this convolution?

% My question is how do I add zero padding to this plot? I'm trying to show the effects of circular convolution with and without zero padding. 
% This part is taking fourier transform of two different functions
a = 0.5;
n = [0,1,2,3,4,5,6,7];
x1 = a.^n;
x2 = [1,1,1,1,1,1,0,0];
X1 = fft(x1,16);
X2 = fft(x2,16);
% Here is the convolution of them. Need to add zero padding for this
% convolution plot
X1X2 = X1.*X2;
x1x2_conv = ifft(X1X2);

Answer 1

[Matt J]

Not sure what the question is, but you can easily compare your result to direct convolution to see if it's correct.

x1x2_conv = ifft(X1X2)

x1x2_conv = 1×16

1.0000 1.5000 1.7500 1.8750 1.9375 1.9688 0.9844 0.4922 0.2422 0.1172 0.0547 0.0234 0.0078 0 -0.0000 -0.0000

conv(x1,x2)

ans = 1×15

1.0000 1.5000 1.7500 1.8750 1.9375 1.9688 0.9844 0.4922 0.2422 0.1172 0.0547 0.0234 0.0078 0 0

[Brianna Miranda]

My question is how do I add zero padding to this plot. I'm trying to show the effects of circular convolution with and without zero padding. This code shows the effect without zero padding but I'm not sure how to add in zero padding.

[Matt J]

You have applied zero padding. To omit zero padding,

X1 = fft(x1);
X2 = fft(x2);