topic Re: Automatically create matrix based on sum of rows and variable in Mathcad in Mathcad

Automatically create matrix based on sum of rows and variable in Mathcad

MC_9370533 — Tue, 24 May 2022 21:05:51 GMT

Hello everyone,

I am trying to automatize a calculation process in Mathcad, but I am having some difficulties doing it.

Lets say I have a matrix with “n x m” number of rows and columns.

In this example we can have the following matrix (5 x 6 – but it can be different, ex: 10 x 15, 9 x 10 etc...):

Note that Ni is each row of the matrix.

There is a variable “var” that can be equal to 1, 2, 3 or 4.

And finally we have vector “V” (that has always 1 single column, but number of rows depends on the variable “var” however this vector is an input, the values below are just an example):

I want to obtain the following matrix “M” depending on the variable “var”:

- If var = 1 (“V” vector will have just 1 row – F1 = 10)

- If var = 2 (“V” vector will have 2 rows – F1 = 10 / F2 = 1)

- If var = 3 (“V” vector will have 3 rows – F1 = 10 / F2 = 1 / F3 = 4)

- Finally if var = 4 (“V” vector will have 4 rows – F1 = 10 / F2 = 1 / F3= 4 / F = 7)

Any suggestions?

Thank you so much for your help,

Miguel

Re: Automatically create matrix based on sum of rows and variable in Mathcad

Werner_E — Wed, 25 May 2022 01:29:41 GMT

Not sure, but is it this what you are looking for?

EDIT: Attached a new screenshot as @terryhendicott had noticed that in the previous one Prime had not displayed the newly created matrices N and V correctly and so the results looked wrong.

Worksheet in P& format attached

Re: Automatically create matrix based on sum of rows and variable in Mathcad

terryhendicott — Wed, 25 May 2022 01:04:07 GMT

The first row of matrix when v = 1 should be

[18 18 63 ....]

[,,,, ...]

Cheers

Terry

Re: Automatically create matrix based on sum of rows and variable in Mathcad

Werner_E — Wed, 25 May 2022 01:35:14 GMT

Good observation, thanks!

Actually the program seems to do the job but for some reason Prime managed to update the creation of the random matrices V and N and using them in the function but did not update the display of N and V. Actually this should never happen (and never did in MC15 and below).

So a hard recalculation of the worksheet fixes this inconsistency which I had not noticed. Thanks for bringing this to my attention.

I attach a new screenshot in my first reply and also attach the worksheet (even though the OP didn't).

Re: Automatically create matrix based on sum of rows and variable in Mathcad

LucMeekes — Wed, 25 May 2022 07:10:01 GMT

So you want to create a specific matrix, namely a vector, from a matrix, a vector and a variable.

If the matrix is this:

The vector is this:

and the variable is 1 you want:

if the variable is 2 you want:

on to, if it is 4 you want:

That can be easily accomplished by this simple function that also works in Prime express:

A numeric example:

Prime 4 file is attached.

Success!
Luc

Re: Automatically create matrix based on sum of rows and variable in Mathcad

LucMeekes — Wed, 25 May 2022 07:03:18 GMT

However, if your vector V always has the length of the value of the variable var, then you don't specifically need var, and the function can become simpler:

And you get:

Prime 4 file attached (You may need to force recalculation of the sheet, to update the symbolic results).

Success!
Luc

Re: Automatically create matrix based on sum of rows and variable in Mathcad

MC_9370533 — Wed, 25 May 2022 08:05:59 GMT

Hello Werner_E,

Yes it's exactly this I was looking for.

Thank you so much for your help.

(Also Terry thank you for your feedback).

Miguel,

Re: Automatically create matrix based on sum of rows and variable in Mathcad

MC_9370533 — Wed, 25 May 2022 08:07:29 GMT

Hello Luc,

I was looking for a solution proposed by Werner_E.

Either way thank you for your feedback.

Miguel,

Re: Automatically create matrix based on sum of rows and variable in Mathcad

LucMeekes — Wed, 25 May 2022 08:39:59 GMT

Ah, I see where I went wrong. A small correction is needed:

Now gives:

and

Which meets your description in the original post.

I understand that that description apparently does not match with what you intended...

Luc