How can I plot a function containing an integral ?

Hey there !

I'm pretty new to Matlab and want to plot a function containing an integral.

The function I want to plot is :

f(s) = 1.05274*exp(integral((0.03-0.000569*exp(0.0824*(s-25))-0.0262139)/2.08773))

with the integral going from value 25 to the value of s.

For that,

1) I first define the X-axis as a vector :

s = linspace(20,100,100)

2) I then define the term inside the integral i.e. (0.03-0.000569*exp(0.0824*(s-25))-0.0262139)/2.08773

fun_a = @(s) (0.03-0.000569*exp(0.0824*(s-25))-0.0262139)/2.08773

3) I define the function f(s)

f = 1.05274*exp(integral(fun_a,25,s))

However, Matlab states "Error using integral (line 85)

A and B must be floating-point scalars." after I input step 3.

Since s is a vector and not a scalar, it doesn't allow me to compute the integral (because the integral is defined from 25 to s)

I just want to tell Matlab that at the X-axis value s=20 for example, I want the function f(s) stated above to take its value for s=20. And this for all values of s between 20 and 100.

Once I have the function, I just want to plot it, with f(s) being the Y-axis and s being the X-axis.

Thank you very much !

Best,

Diego

Answer 1

[darova]

I suggest you to use numerical approach - cumtrapz

clc,clear

x = linspace(1,15,100);
f = 2*x;
sf = cumtrapz(x,f);
plot(x,f)
line(x,sf)
line(x,x.^2+5)
legend('original 2x','cumtrapz x^2','x^2')

[Diego San Roman]

Worked like a charm. Thanks !