Skip to main content
P
ptc-46926961-Visitor
1-Visitor
March 28, 2013
Solved

Complex Summation Problem

  • March 28, 2013
  • 2 replies
  • 3428 views

Everyone,

I am trying to set up a summation equation the that uses a combination of a current instance of a variable as well as the previous one. Anyone have any idea on how I would set this up?

equation.png

Thank you

Best answer by Werner_E

Which version of Mathcad do you use?

I guess you are not aware of the fact that Mathcad has two different types of indices.

You seem to be using the so called literal index - typing v dot i (or v "Strg & dash" in Prime) to get it. This is only a name, only to look different as v1. Is has nothing to do with adressing vectors or matrices.

The matrix index we need here you get by typing v[i or you find it in the matrix palette, too.

Edited: I have seen from your other reply that you are using Prime. I attached the sheet in that format here: http://communities.ptc.com/message/201007#201007

2 replies

W
Werner_E25-Diamond I
25-Diamond I
March 28, 2013

Please post a Mathcad sheet with your current attempts. You have better chances of somebody taking care of cour question that way, as it shows which version of Mathcad you intend to use and it saves us the redious retyping work.

In your pic the definition of R and N are missing. Or should phi be function of the two?

In your case you would first define a nd B, either calculate them or set them up as functions of R and N if they should remain unknown.

Then create the vector v. As Mathcad by default begins with index 0, I would switch you formulas by +1 (this will also affect the summation, of course). j is running from 0 to n-2, I guess, as the las v used in summation is v index n-1?

Now you can setup the formula for phi, either as a function of R and N or as a constant.

P
ptc-46926961-VisitorAuthor
1-Visitor
March 28, 2013

Thank you for the assistance. n, N and R are all calculated else where

I have attempted what you suggestec but I am still having difficulty with defining previous instance of the variable. I have attached my latest attempy

W
Werner_E25-Diamond I
25-Diamond I
March 28, 2013

OK, I see you are using Prime.

I converted my sheet, which was made in Mathcad 15, and attach it here.

As already assumed, your problem were the different types of indices.

W
Werner_E25-Diamond I
25-Diamond I
March 28, 2013

Would this help?

summation1.png

or this?

summation2.png

P
ptc-46926961-VisitorAuthor
1-Visitor
March 28, 2013

Both options look valid to me

I guess where I am struggling is that I can't seem to create j-1 subscript. Is there a trick for doing this? Every time I add the the minus sign it places it in as part of the equation.

Thanks

W
Werner_E25-Diamond IAnswer
25-Diamond I
March 28, 2013

Which version of Mathcad do you use?

I guess you are not aware of the fact that Mathcad has two different types of indices.

You seem to be using the so called literal index - typing v dot i (or v "Strg & dash" in Prime) to get it. This is only a name, only to look different as v1. Is has nothing to do with adressing vectors or matrices.

The matrix index we need here you get by typing v[i or you find it in the matrix palette, too.

Edited: I have seen from your other reply that you are using Prime. I attached the sheet in that format here: http://communities.ptc.com/message/201007#201007

Terms & ConditionsAccessibility statement