### Right choice for a dictionary of matrices with non constant coefficients.

Hi,

K is any field.

I need to store matrices in a dictionary.

Some of them have constant coefficients in K (let M1 be such a matrix),
and some have non constant coefficients, say these coeffcients are functions from t to K (let M2 be such a matrix).

I need to get M2 from the dictionary, and then be able to manipulate it as if it was a function of t.

(T) In particular, I need to be able to manipulate the matrices obtained from M2 by setting t to be equal to some specific values.

Since my functions are polynomials for now, I have tried doing something like this:

```
var('t')
sample = {}
sample[('M1')] = matrix(QQ, 2, [7, 5, 2, 4])
sample[('M2')] = matrix(QQ['t'], 2, [t^2, 2, 3, 1 - t])
```

But then I don't know how to proceed to perform the task (T).
And I have the feeling that there are much better options.

What should I do?

Thanks.