Please help me

[dbayasgalan]

[StuartBruff · Accepted solution]

Damdinsvren Bayasgalan wrote:

I think you may need the C vectors in row form rather than column form to make the matrices conformable. The way you have implemented it, C is a nested array rather than a matrix.  Perhaps this is nearer what you want? ...

Stuart

[dbayasgalan]

[RichardJ]

The way you have defined C, it is a vector of vectors. You cannot use such a structure in normal matrix math. If what Stuart shows is not what you want, please explain, in words, what you are trying to do.

[dbayasgalan]

truss structure analysis

[RichardJ]

Sorry, but that is not a useful answer. If you cannot explain what you want to do is a useful way, then it's not possible for us to tell you how to do it.

[StuartBruff]

Can you scan in (web copy&paste), from you source material, a picture of the equations that you want to multiply?

Stuart

[dbayasgalan]

[RichardJ]

That is what Stuart shows, and the answers are the same (other than the sign; you are missing a minus in front of the S matrix), just laid out differently.

[StuartBruff]

As Richard says, you have a vector of vectors.  Each element of an array (vector or matrix) can have another array as one of its elements - which is what you've got with you definition of C.   Mathcad will try to multiply your 7x5 "S" matrix with the 5x1 "C" matrix, and raises an error as Mathcad's matrix multiplication routine only allows numbers in each element (and not arrays or strings, for example) ... In principle, you could multiply nested arrays together, provided you define what you mean by such multiplication.   Here's an example that applies very basic matrix multiplication to each element of two matrices (it's only a quick demo, not a thought-out function!!!).

I suspect that what you want is what I originally posted, however, and you need to rearrange your C.n elements into columns as shown.

Stuart