12-Amethyst

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is there a way to get the Lamberth W function?

Forum|Forum|9 years ago
May 25, 2016
5 replies
9248 views

HI,

We would need the Lambert W function. IN Mathematica it is ProductLog(x) and in Maple W.

When could this important function be get in Mathcad 15 or Prime ?

Thanks

Walter

Other

Best answer by StuartBruff

WALTER SCHRABMAIR wrote:

HI,

We would need the Lambert W function. IN Mathematica it is ProductLog(x) and in Maple W.

When could this important function be get in Mathcad 15 or Prime ?

Thanks

Walter

It already exists in Mathcad 15 ...

Stuart

W

WalterSchrabmai

Author

12-Amethyst

Found: https://community.ptc.com/t5/PTC-Mathcad/Lambert-s-W-function/m-p/298293#57489

But unfortunately it`s just an approximation, but a good one.

Thanks

W

WalterSchrabmai

Author

12-Amethyst

also good to know: http://www.sciencedirect.com/science/article/pii/S1369703X12000277

V

VladimirN

24-Ruby III

For those interested - the article in the attachment.

1_Article.pdf

V

VladimirN

24-Ruby III

Hi,

You can use the following built-in Mathcad functions:

LambertW(x) - Lambert's W function;
LambertW(n,x) - nth branch of Lambert's W function. Note that LambertW(x) = LambertW(0,x).

And this themes may also be of interest to you:

Author

12-Amethyst

Thanks Vladimir!

V

VladimirN

24-Ruby III

Walter,

Please change the "Correct Answer" is not to introduce other people astray (which will also look for the answer to this question in the future).

S

StuartBruff

Answer

23-Emerald V

WALTER SCHRABMAIR wrote:

HI,

We would need the Lambert W function. IN Mathematica it is ProductLog(x) and in Maple W.

When could this important function be get in Mathcad 15 or Prime ?

Thanks

Walter

It already exists in Mathcad 15 ...

Stuart

W

WalterSchrabmai

Author

12-Amethyst

Thanks a lot!!!!! Greetings, Walter

S

StuartBruff

23-Emerald V

No problem, Walter. Although I think Werner's solve block solution is probably a better route to go for repeated working within a worksheet (eg, for large vectors) as the symbolic solution occupies quite a bit of space (alternatively, put LambertW evaluations into an Area and hide the Area).

Stuart

W

Werner_E

25-Diamond I

Is was already said that LambertW exists in Mathcad for symbolic evaluations and that we can use it for numeric evaluations in some way.

I remember threads a long time ago where it was tried to create true numeric functions based on functions which only are available in the symbolics, like LambertW.

As far es I remember there was no real success as ever so often we would experience rather strange effects.

Here is one try which on first sight looks pretty OK

But trying to uses this function in a plot fails

On further investigation it gets really strange

Sometimes there is a workaround using a dummy numeric eval, but its pretty clear, that LW() can't be used as a normal numeric function

So I guess that it will be often the better choice to use a user written function like the one of Stuart you referred to.

Maybe even a solve block function would do the job in a satisfactory way (the following at least for arguments greater that -1/e so the result is real)