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surya93jith1-Visitor
1-Visitor
December 3, 2017
Question

Nested For loop and If programming Help

  • December 3, 2017
  • 3 replies
  • 2188 views

Hi,

Herewith, I have attached the problem (mcdx file) that I am having trouble with.

I have a vector C with 105 elements in it
I have another function x(y) with 'y' varying from 0 to 1 with a stepsize of 0.001 (Vector with 1000 elements in it)

I want to find out which value of 'y' would give the resulting value of 'x' which matches the element in C. Therefore, I need to create a matrix M3 (105 Elements) with 'y' that was found out before for that particular value of C and x.

For example The first element in C is 0.184. The y value 0.635  results in x = 0.184, matching C. So the first element of my M3 matrix is 0.635.
Please refer to the attached MATHCAD file for the problem.
Thank You!

3 replies

D
DJF16-Pearl
16-Pearl
December 3, 2017

While I didn't spend a lot of time on it, I don't think your approach will work.  Basically because of errors - You are looking at specific intervals and hoping they match up with the C value.  They won't unless you specifically round them off to a few digits.  But that's a poor way of doing it anyway. You can solve the equation directly (4 possible answers, 1 seems to match your example so I went with it).  Then a simple solve block and a program to call it for each row.  See PDF.

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
December 4, 2017

The function "match" gives you the ability to modify.

 

I can't open your file (I'm stuck at Prime 3.0), but have you tried

       DX[i := match(C[i,Y,X,"near")  ??

L
LucMeekes23-Emerald IV
23-Emerald IV
December 4, 2017

You say you're working with vectors, but you are not.

M1 = x is a range (from 0.8, in steps of 0.05 up to 5.

With all the calculation that follows, the result is that the value C that you want to find a 'y' value for is also a range.

If you restructure your sheet to use functions and/or real vectors (stuff that you can access individual elements of by indexing) it becomes very easy to find 'y' value for any given x-value through the difinition of C, namely:

 

i:=0,1...105

M3[i:=root(C(y)-x[i,y,0.8,5)

 

Where it is assumed that C is defined as a function of y: C(y).

 

I leave it up to you to change the worksheet; the way it is structured now makes it difficult for me to discern what  are constants, what are functions and what are results of those functions.

If you have problems after that, don't hesitate to come back (in this same thread).

 

Success!
Luc

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