Hi

On Jun 5, 2017, at 4:33 AM, Moshe Kelner <MOSHEKE at cellcom.co.il> wrote:

Hi ,

I'm asking for a way to compute the integral of:  

function(x) {x*(log(x)+b)*((log(x)+b)^(a-1)-b^(a-1))/(a-1)*(b^(a-1)}

Problems here ----------------^^^-----and if(a==1)-----^^^---paren--^
                              |||                      |||         |

Annotation only useful with monospaced font. Not likely to be useful to Moshe if he will be using HTML for posting.

When a and b are between 1 to 10 and X is the integral parameter between 0 to 1 '

How are you planning to handle a value of log(0)? Or for that matter division by 0 if a==1

R does do limiting integrations (if that is the correct term for lim(integrate(func, lower=0, ...)) with the value of func(0) undefined. You may need to set the lower limit of integration to be a small positive number.

R also has difficulties with fractional powers of negative numbers:

(-.2)^(1.1-1)

[1] NaN 

Did you perhaps intend `a` to be in the set: 2:9 ?

If I set: 

 my_f <- function(x, a=1.1, b=1.1)   # will error out with those defaults
                    {x*(log(x)+b)*((log(x)+b)^(a-1)-b^(a-1))/(a-1)*(b^(a-1))}

integrate(my_f, lower=0.1,upper=.9, a=2, b=2)  #call with integer `a` and `b`

-0.5063435 with absolute error < 4.6e-09

integrate(my_f, lower=0.01,upper=.9, a=2, b=2)

-0.4829606 with absolute error < 3.5e-05

integrate(my_f, lower=0.001,upper=.9, a=2, b=2)

-0.4813907 with absolute error < 4.8e-05

Moshe

excised meaningless confidentiality message

Thank You.
http://www.cellcom.co.il

	[[alternative HTML version deleted]]

Do read the Posting Guide which advises not to use HTML.

______________________________________________
R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

David Winsemius
Alameda, CA, USA