# How to express inner product of two vectors in Stateflow action language?

2 views (last 30 days)
Wilfred on 11 Nov 2011
I want to compute the inner product y of two vectors u and v (same size, both based on input from Simulink) in Stateflow action language. I have tried
x=ml.transpose(u)
y=ml.(x*v)
but during compilation this results in a coder error "Cannot reshape Local Data 'x' (#...) ([...]) to Local Data 'y' (#...) (scalar) for operator =. Please refer to object (#...)." Apparently, the "ml." notation only works with functions, not with operators such as '*'. Would there be a way to write a product as a function - something like y=ml.product(x,v)?
An alternative might be
x=ml.transpose(u)
y=ml('x*v')
but this requires x and v to be defined in the Matlab workspace, which would mean I have to export them first. This seems to be a rather laborious solution.
Any ideas?
Wilfred on 14 Nov 2011
I should have mentioned that both u and v are composed of integers. However, it seems that solutions are not available in that case, let's assume that u and v are composed of real numbers, as integers can of course also be converted to real numbers.

Kaustubha Govind on 11 Nov 2011
Try the function times for inner product of two vectors.
Wilfred on 14 Nov 2011
This was not exactly what I was looking for, but it helped me solve my problem. The function "times" multiplies input arrays element by element and puts these in a vector the same size as the input vectors (with no need for transposing one of them as I initially tried). What I wanted was a scalar equal to the sum of the element-by-element multiplications, which can of course be computed from it:
y=ml.sum(ml.times(u,v))
Wilfred on 14 Nov 2011
And, by the way, Thanks!!!

Walter Roberson on 11 Nov 2011
The MATLAB * operator has the formal name mtimes
Wilfred on 14 Nov 2011
Thanks, this works too, if put this way:
y=ml.mtimes(ml.transpose(u),v)
Here, the order of listing the arguments is important.

### Categories

Find more on Simulink Functions in Help Center and File Exchange

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!