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MC_93705338-Gravel
8-Gravel
May 24, 2022
Solved

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

  • May 24, 2022
  • 3 replies
  • 4065 views

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...):

MC_9370533_0-1653424839493.png

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):

MC_9370533_6-1653425383586.png

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)

MC_9370533_2-1653425330437.png

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

MC_9370533_3-1653425330443.png

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

MC_9370533_4-1653425330445.png

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

MC_9370533_5-1653425330447.png

Any suggestions?

 

Thank you so much for your help,

 

Miguel

Best answer by Werner_E

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).

3 replies

W
Werner_E25-Diamond I
25-Diamond I
May 25, 2022

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

Werner_E_0-1653441990664.png

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

    T
    21-Topaz II
    terryhendicott21-Topaz II
    21-Topaz II
    May 25, 2022

    Hi

    The first row of matrix when v = 1 should be

    [18  18  63 ....]

    [,,,,              ...]

    Cheers

    Terry

      W
      Werner_E25-Diamond IAnswer
      25-Diamond I
      May 25, 2022

      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).

        L
        LucMeekes23-Emerald IV
        23-Emerald IV
        May 25, 2022

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

        If the matrix is this:

        LucMeekes_0-1653460924838.png

        The vector is this:

        LucMeekes_1-1653460944843.png

        and the variable is 1 you want:

        LucMeekes_2-1653460965173.png

        if the variable is 2 you want:

        LucMeekes_3-1653460986688.png

        on to, if it is 4 you want:

        LucMeekes_4-1653461050097.png

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

        LucMeekes_5-1653461084541.png

        A numeric example:

        LucMeekes_6-1653461114786.pngLucMeekes_7-1653461119305.png

        LucMeekes_10-1653461168467.png

        LucMeekes_11-1653461196933.png

         

        LucMeekes_9-1653461140477.png

        Prime 4 file is attached.

         

        Success!
        Luc

         

         

         

        M
        MC_93705338-GravelAuthor
        8-Gravel
        May 25, 2022

        Hello Luc,

         

        I was looking for a solution proposed by Werner_E.

         

        Either way thank you for your feedback.

         

        Miguel,

        L
        LucMeekes23-Emerald IV
        23-Emerald IV
        May 25, 2022

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

        LucMeekes_0-1653467858148.png

        Now gives:

        LucMeekes_1-1653467875211.png

        and

        LucMeekes_2-1653467891050.png

        Which meets your description in the original post.

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

         

        Luc

        L
        LucMeekes23-Emerald IV
        23-Emerald IV
        May 25, 2022

        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:

        LucMeekes_16-1653462082240.png

        And you get:

        LucMeekes_13-1653461791000.png

        LucMeekes_14-1653461797922.png

        LucMeekes_15-1653461805338.png

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

         

        Success!
        Luc

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