## Feature #14116

### Add Matrix #exponentiate method as Matlab's exp

**Description**

Add exponentiate method which results in returning a new matrix with each element being an exponent of the number e.

Here is PR for that: https://github.com/ruby/ruby/pull/1762

#### Updated by greggzst (Grzegorz Jakubiak) over 2 years ago

**Subject**changed from*Add Matrix #exponentiate method*to*Add Matrix #exponentiate method as Matlab's exp*

#### Updated by marcandre (Marc-Andre Lafortune) over 2 years ago

**Assignee**set to*marcandre (Marc-Andre Lafortune)***Status**changed from*Open*to*Feedback*

Thanks for the PR.

The name is not acceptable, as the exponential of a matrix is something different (expm in Matlab): https://en.wikipedia.org/wiki/Matrix_exponential

I wish I was more familiar with machine learning to know how frequent calculating this is. If it is, there should be a name for this, no?

The fact that `map{|e| Math.exp(e)}`

is quite simple to do makes me even more hesitant to add that method too.

#### Updated by MSP-Greg (Greg L) over 2 years ago

marcandre (Marc-Andre Lafortune) wrote:

Thanks for the PR.

The name is not acceptable, as the exponential of a matrix is something different

I agree. Not quite a single line method. Maybe something like `entrywise_exp`

or `entrywise_exponential`

like in 60860. But as you mentioned, 'is quite simple'...

#### Updated by shevegen (Robert A. Heiler) over 2 years ago

Once again it is back to the oldest problem in computer technology - giving things a proper name. :-)

#### Updated by greggzst (Grzegorz Jakubiak) over 2 years ago

marcandre (Marc-Andre Lafortune) wrote:

Thanks for the PR.

The name is not acceptable, as the exponential of a matrix is something different (expm in Matlab): https://en.wikipedia.org/wiki/Matrix_exponential

I wish I was more familiar with machine learning to know how frequent calculating this is. If it is, there should be a name for this, no?

The fact that

`map{|e| Math.exp(e)}`

is quite simple to do makes me even more hesitant to add that method too.

I changed the name to entrywise_exp as suggested. True about the simplicity but it would be a good shorthand taking into consideration fact that it is used in many cases e.g. multivariate normal distribution.