Fourier Transformation

clear all
close all
clc
w1=-10:0.1:10
t=-10:0.1:10
x=exp(-t)
subplot(1,2,1)
plot(t,x)
m=1
for w=-10:0.1:10
    i=1
    sum=0
    for t=-10:0.1:10
        dt=0.1
        sum=sum+(x(i).*(exp(-j*w*t).*dt))
i=i+1
    end
    X(m)=sum
    m=m+1
end
y1=abs(X)
subplot(1,2,2)
plot(w1,y1)