topic Re: Create a matrix with Partial derivative with more variables in Mathcad

Create a matrix with Partial derivative with more variables

TG_14487572 — Mon, 02 Feb 2026 20:14:39 GMT

PTC Mathcad Prime 8.0.0.0

I have a function that depends on several variables, and I want to compute the partial derivative with respect to each variable and store the results in a matrix.

For example, the variables R1,R2,R3,R4,R5,R6,R7, and R8 are known.

F(R1, R2, R3, R4, R5, R6, R7, R8)=R5*R4/(R3+R4) +(R7-R8/2)*R1+R6/R2

I would like to create a matrix A_dif such that:

A_dif(1)= dF/dR1

A_dif(2)= dF/dR2

………………..

A-dif (8)=dF/dR8

Can this be done so we do not need to repeat the operation 8 times.

Re: Create a matrix with Partial derivative with more variables

Fred_Kohlhepp — Tue, 03 Feb 2026 13:13:59 GMT

You can. It's a lot of typing!.

Re: Create a matrix with Partial derivative with more variables

TG_14487572 — Tue, 03 Feb 2026 13:57:27 GMT

I had this as a solution, but I was expecting something that uses a for‑statement, because sometimes my functions have 100 variables. I would like to automate the process.

Re: Create a matrix with Partial derivative with more variables

Werner_E — Tue, 03 Feb 2026 13:58:25 GMT

This is what the Nabla/Gradient operator is to be used for. Can be used symbolically but also numerically

Re: Create a matrix with Partial derivative with more variables

Werner_E — Tue, 03 Feb 2026 14:20:14 GMT

A function with 100 arguments?

So these arguments better are provided via an input vector instead of listing them individually.

As an example the same demo function with three arguments as posted before

P.S.: I am not sure if the gradient operator already exists in Prime 8, though.

EDIT: I just check and it seems that the gradient operator was not present in Prime 8

See: Solved: Representing Del Operations [curl(u), div(u), grad... - PTC Community

The operator actually was introduced in Prime 9.

Any chance you can upgrade your version of Prime?

Re: Create a matrix with Partial derivative with more variables

TG_14487572 — Tue, 03 Feb 2026 19:56:58 GMT

Hi Werner,

I have PTC Mathcad Prime 8.0.0.0 which does not have this operator that you suggested.

I have done the same way what was suggested by Fred but I want no to copy and pass 100 time if I have bigger function.

Re: Create a matrix with Partial derivative with more variables

Werner_E — Tue, 03 Feb 2026 21:55:09 GMT

@TG_14487572 wrote:

Hi Werner,

I have PTC Mathcad Prime 8.0.0.0 which does not have this operator that you suggested.

I have done the same way what was suggested by Fred but I want no to copy and pass 100 time if I have bigger function.

Yes, I later noticed that the gradient operator was only introduced in Prime 9. See also my second answer above and the link provided there.
I'm afraid that there will be no convenient option in your version of Prime, as Prime does not provide all the necessary features—it does not allow vector elements as derivative variables and, unlike the old, genuine Mathcad, it does not allow symbolic evaluations within a program.
So if you don't have the option of upgrading to a newer version of Prime, it will probably be difficult or rather impossible to achieve.

As a supplement to what was shown earlier: If partial differentiation is to be performed for all variables, it is not necessary to list all variables individually in the Nabla operator; instead, the corresponding placeholder can be left empty in this case:

Re: Create a matrix with Partial derivative with more variables

TG_14487572 — Tue, 03 Feb 2026 22:08:39 GMT

Hi Werner,

my colleagues had used gradient before but after upgrading to PTC Mathcad Prime 8.0.0.0 it disappeared. I never expect that a new version will not open an old one and will have smaller capability, but ... C'est la vie!

Thank you for your time!

Re: Create a matrix with Partial derivative with more variables

Werner_E — Tue, 03 Feb 2026 22:47:32 GMT

@TG_14487572 wrote:

Hi Werner,

my colleagues had used gradient before but after upgrading to PTC Mathcad Prime 8.0.0.0 it disappeared. I never expect that a new version will not open an old one and will have smaller capability, but ... C'est la vie!

Thank you for your time!

To the best of my knowledge no Prime version below version 9 provided gradient operator.

But of course legacy Mathcad did. But switching from legacy Mathcad to Prime is not an upgrade but rather a downgrade in usability and functionality 😞

Re: Create a matrix with Partial derivative with more variables

Werner_E — Wed, 04 Feb 2026 07:22:06 GMT

OK, I gave it a try and here is my best approach to automatically get all partial derivatives without using the gradient operator.

The method sure has its drawbacks and if ever possible you should switch to Prime 9 or higher where the gradient operator is available.

The attached file is in Prime 11 format as I don't have Prime 8 installed. However, you can certainly follow it based on the screenshot.

Hope it works OK in Prime 8 and can be of help.

Re: Create a matrix with Partial derivative with more variables

LucMeekes — Wed, 04 Feb 2026 07:44:45 GMT

Werner's file converted to Prime 8. I had to take the gradients out, as they wouldn't convert.

Success!
Luc

Re: Create a matrix with Partial derivative with more variables

TG_14487572 — Wed, 04 Feb 2026 22:23:18 GMT

Hi Werner,

Thank you for the solution!!!

I need to type now only f(xo,x,1, ....Dn-1) to make it work for different number of variables.

If I can do something that automatically can populate f(xo,x,1, ....Dn-1), it will be great.

Re: Create a matrix with Partial derivative with more variables

TG_14487572 — Wed, 04 Feb 2026 22:24:13 GMT

Thank you!!!

Re: Create a matrix with Partial derivative with more variables

Werner_E — Wed, 04 Feb 2026 23:23:23 GMT

I need to type now only f(xo,x,1, ....Dn-1) to make it work for different number of variables.

No idea what you are talking about!

Could it be that you attached the wrong file?

Re: Create a matrix with Partial derivative with more variables

Fred_Kohlhepp — Thu, 05 Feb 2026 02:42:48 GMT

I'm using Express, and Jacobian is not available, but I think it may give you what you're looking for.

Re: Create a matrix with Partial derivative with more variables

Werner_E — Thu, 05 Feb 2026 04:32:00 GMT

Its not how 'Jacob' usually would be used for but IMHO its a pretty good idea to use it here and i would say that's the way to go.

It should be available in Prime 8.

Unfortunately it still does need a vector function.