ts=0.2;
fs=1/ts;
df=0.01;
x=[zeros(1,10),[0:0.2:1],ones(1,9),[1:-0.2:0],zeros(1,10)];
[X,x,df1]=fftseq(x,ts,df);
X1=X/fs;
f=[0:df1:df1*(length(x)-1)]-fs/2;
f1=[-2.5:0.001:2.5];
y=4*(sinc(2*f1)).^2-(sinc(f1)).^2;
pause
clf
subplot(2,1,1)
plot(f1,abs(y));
title('magnitude of x(t)')
xlabel('frequency')
pause
subplot(2,1,2)
plot(f,fftshift(abs(X1)));
xlabel('frequency')
title('magnitude of x(t) numically')