nushell/docs/commands/histogram.md
Joseph T. Lyons 3239e5055c
Added a count column on the histogram command (#1853)
* Adding iniitial draft for the addition of the count column on the histogram command

* Update histogram documentation

* Add count column test to histogram command

* Fix error in histogram documentation
2020-05-20 18:02:36 +12:00

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# histogram
Creates a new table with a histogram based on the column name passed in.
Syntax: `histogram <column_name> ...args`
### Parameters
* `<column-name>`: name of the column to graph by
* `args`: column name to give the histogram's frequency column
## Examples
Let's say we have this file `random_numers.csv` which contains 50 random numbers.
**Note**: The input doesn't have to be numbers it works on strings too. Try it out.
```shell
> open random_numbers.csv
────┬────────────────
# │ random numbers
────┼────────────────
01
12
22
...
475
485
491
────┴────────────────
```
If we now want to see how often the different numbers were generated, we can use the `histogram` function:
```shell
> open random_numbers.csv | histogram "random numbers"
───┬────────────────┬───────┬──────────────────────────────────────────────────────────────────────────────────────────────────────
# │ random numbers │ count │ frequency
───┼────────────────┼───────┼──────────────────────────────────────────────────────────────────────────────────────────────────────
001 │ ******
1115 │ ****************************************************************************************************
2210 │ ******************************************************************
337 │ **********************************************
449 │ ************************************************************
558 │ *****************************************************
───┴────────────────┴───────┴──────────────────────────────────────────────────────────────────────────────────────────────────────
```
We can also set the name of the second column or sort the table:
```shell
> open random_numbers.csv | histogram "random numbers" probability
───┬────────────────┬───────┬──────────────────────────────────────────────────────────────────────────────────────────────────────
# │ random numbers │ count │ probability
───┼────────────────┼───────┼──────────────────────────────────────────────────────────────────────────────────────────────────────
001 │ ******
1115 │ ****************************************************************************************************
2210 │ ******************************************************************
337 │ **********************************************
449 │ ************************************************************
558 │ *****************************************************
───┴────────────────┴───────┴──────────────────────────────────────────────────────────────────────────────────────────────────────
```
```shell
> open random_numbers.csv | histogram "random numbers" probability | sort-by probability
───┬────────────────┬───────┬──────────────────────────────────────────────────────────────────────────────────────────────────────
# │ random numbers │ count │ probability
───┼────────────────┼───────┼──────────────────────────────────────────────────────────────────────────────────────────────────────
001 │ ******
137 │ **********************************************
258 │ *****************************************************
349 │ ************************************************************
4210 │ ******************************************************************
5115 │ ****************************************************************************************************
───┴────────────────┴───────┴──────────────────────────────────────────────────────────────────────────────────────────────────────
```
Of course, histogram operations are not restricted to just analyzing numbers in files, you can also analyze your directories
```shell
> ls -fa | histogram type | sort-by count
───┬─────────┬───────┬──────────────────────────────────────────────────────────────────────────────────────────────────────
# │ type │ count │ frequency
───┼─────────┼───────┼──────────────────────────────────────────────────────────────────────────────────────────────────────
0 │ Symlink │ 8 │ *****************
1 │ File │ 9 │ ********************
2 │ Dir │ 45 │ ****************************************************************************************************
───┴─────────┴───────┴──────────────────────────────────────────────────────────────────────────────────────────────────────
```