How can I solve the problem in integral code?

Solve the problem

Answer 1

[Torsten]

Loop over the values of the sigma-vector - thus call "vpaintegral" for each sigma value separately.

Or alternatively make your code a function and call it from a script with a single sigma-value as input.

Further, I'd recommend first to use "integral" instead of "vpaintegral" to save computation time.

And where do you compute w1 - w6 - the variables you try to plot at the end of your code ?

Works because "vpaintegral" is called for each sigma-value separately:

syms r
f = r^2;
sigma = 0:0.1:1;
arrayfun(@(sigma)vpaintegral(f,r,0,sigma),sigma)

ans = 

Does not work because "vpaintegral" is called once with the complete sigma-vector:

syms r
f = r^2;
sigma = 0:0.1:1;
vpaintegral(f,r,0,sigma)

Operands to the logical AND (&&) and OR (||) operators must be convertible to logical scalar values. Use the ANY or ALL functions to reduce operands to logical scalar values.

Error in sym/vpaintegral (line 182)
(isinf(b) && isempty(symvar(b)) && ~isreal(b))

[Shreen El-Sapa]

[Torsten]

It's the same problem as above. "vpaintegral" can integrate one function over one interval of integration at a time. Thus alpha must be a single value when you call "vpaintegral", not a vector of values.

[Shreen El-Sapa]

Thanks I will try to use it.

[Shreen El-Sapa]

Excuse me, Can I do this for 6 integrals?

[Shreen El-Sapa]

please see this:

[Torsten]

Try the attached revised code.

[Walter Roberson]

Note that vpaintegral() can handle the case where the part to be integrated is non-scalar, but cannot handle the case where the limits to integration are non-scalar.

syms x
vpaintegral([sin(x), cos(x)], x, [0 1])

ans = 

[Torsten]

@Walter Roberson

Thank you for the info.

@Shreen El-Sapa

So the changes to your last code (test_microstrength.m) were not necessary (except for the final plotting).