Database Reference
In-Depth Information
How to do it…
Similar to how we use
$
in order to select columns, there are several ways in which we can
use it to select rows, shown as follows:
1.
We can create a sequence of the values of one row using
$
, and pass it the index of
the row we want as well as passing
:all
for the columns:
user=> (i/$ 0 :all chn-data)
("AG.AGR.TRAC.NO" "684290" "738526" "52661" "" "880859" "" "" ""
"59657" "847916" "862078" "891170" "235524" "126440" "469106"
"282282" "817857" "125442" "703117" "CHN" "66290" "705723"
"824113" "" "151281" "669675" "861364" "559638" "191220" "180772"
"73021" "858031" "734325" "Agricultural machinery, tractors"
"100432" "" "796867" "" "China" "" "" "155602" "" "" "770629"
"747900" "346786" "" "398946" "876470" "" "795713" "" "55360"
"685202" "989139" "798506" "")
2.
We can also pull out a dataset containing multiple rows by passing more than one
index into
$
with a vector (There's a lot of data, even for three rows, so I won't show
it here):
(i/$ (range 3) :all chn-data)
3. We can also combine the two ways to slice data in order to pull speciic columns and
rows. We can either pull out a single row or multiple rows:
user=> (i/$ 0 [:Indicator-Code :1992] chn-data)
("AG.AGR.TRAC.NO" "770629")
user=> (i/$ (range 3) [:Indicator-Code :1992] chn-data)
| :Indicator-Code | :1992 |
|-------------------+--------|
| AG.AGR.TRAC.NO | 770629 |
| AG.CON.FERT.PT.ZS | |
| AG.CON.FERT.ZS | |
How it works…
The
$
macro is the workhorse used to slice rows and project (or select) columns from
datasets. When it's called with two indexing parameters, the irst is the row or rows and
the second is the column or columns.
