[R] Hi

David Winsemius dwinsemius at comcast.net
Mon Jun 5 18:31:28 CEST 2017

> 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

> 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.
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David Winsemius
Alameda, CA, USA

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