Database Reference
In-Depth Information
3.
Now that it's a matrix, we can treat it like a sequence of rows. Here, we pass it to
first
in order to get the irst row,
take
in order to get a subset of the matrix,
and
count
in order to get the number of rows in the matrix:
user=>
(first va-matrix)
A 1x3 matrix
-------------
8.19e+03 4.27e+03 2.06e+03
user=>
(count va-matrix)
591
4.
We can also use Incanter's matrix operators to get the sum of each column, for
instance. The
plus
function takes each row and sums each column separately:
user=> (reduce plus va-matrix)
A 1x3 matrix
-------------
5.43e+06 2.26e+06 1.33e+06
How it works…
The
to-matrix
function takes a dataset of loating-point values and returns a compact
matrix. Matrices are used by many of Incanter's more sophisticated analysis functions,
as they're easy to work with.
There's more…
In this recipe, we saw the
plus
matrix operator. Incanter deines a full suite of these. You can
learn more about matrices and see what operators are available at
https://github.com/
See also…
F
The
Selecting columns with $
recipe in this chapter has more information on how to
select speciic columns from a dataset