I want to integrate a function

i want to integrate this function used quad function but giving error

kindly resolve

[Walter Roberson]

Your code is

function Ix = f(x)
global Lz  cr2 n1  n2
%wq = x.*x *cr2/(2 * Lz*Lz);
wq = x; 
f5 = fbjnn(x,n1,n2);
 Ix = (x.^3).*f5;
end

We do not have values for those global variables, and we do not have your fbjnn function, so we are not able to test the code.

What error message is given?

[Torsten]

Can "fbjnn" handle vector inputs for x ?

Answer 1

[reshma nesargi]

kindly go through the entire program and help me sought out the problem.

fbjnn is the function written to calculate the formula given in untitled file.

Answer 2

[reshma nesargi]

the program worked error free from 2,3 days all of a sudden since yesterday it is giving the error like this

not understanding what the problem is

Error using .^

Arrays have incompatible sizes for

this operation.

Error in fbjnn (line 11)

fz = exp(-z).* (z.^k);

Error in f (line 6)

f5 = fbjnn(x,n1,n2);

Error in quad (line 67)

y = f(x, varargin{:});

Error in Bulk (line 32)

Ix = quad('f',0,100);

[Torsten]

z and k are incompatible in size.

That's why I asked whether fbjnn can deal with vector input. This shows: it can't.

Use "integral" instead of "quad" and call it with the option 'ArrayValued',true :

Ix = quad('f',0,100);        -> Ix = integral(@f,0,100,'ArrayValued',true);
Iz = quad('fun',0,100);      -> Iz = integral(@fun,0,100,'ArrayValued',true);

Answer 3

[reshma nesargi]

Thank you but what is meant by 'ArrayValued' should we give some value there or write as it is what ever you have suggested

[Walter Roberson]

'ArrayValued',true is a "name/value pair" that should be written exactly as Torsten showed.

Answer 4

[reshma nesargi]

on substituting quad with integral it gave this error

Warning: Minimum step size reached

near x = 6.284. There may be a

singularity, or the tolerances may

be too tight for this problem.

> In integralCalc/checkSpacing (line 467)

In integralCalc/iterateArrayValued (line 215)

In integralCalc/vadapt (line 130)

In integralCalc (line 75)

In integral (line 87)

In Bulk (line 36)

Unable to perform assignment

because the indices on the left

side are not compatible with the

size of the right side.

Error in Bulk (line 59)

cmb(i+1) = (pref *sumn2)/(9*10^11);

Answer 5

[Walter Roberson]

global Lz  cr2 n1  n2

Uh-oh... caution time.

Lz = 1*10^-06;
cr2 = (hc * c)/(ec * b);

Okay, the globals Lz and cr2 are defined.

for i = 0:1:20
    t(i+1)=i;
    bkt=kB*t(i+1);

    Ix = integral(@f, 0, 100, 'arrayvalued', true)

Okay, what does f do?

    
function Ix = f(x)
global Lz  cr2 n1  n2
%wq = x.*x *cr2/(2 * Lz*Lz);
wq = x; 
f5 = fbjnn(x,n1,n2);
 Ix = (x.^3).*f5;
end

... f uses the global variables n1 and n2 that are not defined.

[reshma nesargi]

Sir n1 and n2 are defined in the main program "Bulk" it come in the for loop

[Walter Roberson]

Show us the lines that assign values to n1 and n2 in Bulk.

[reshma nesargi]

N1 and N2 comes in the for loop of the main program Bulk. I was trying to call the quad function outside the for the so may be the value of N1 and N2 were not reaching it. Now i tried calling it with in the for loop it worked.

thankq very much for all your suggestions to get through this.

thanks much