nushell/docs/commands/math.md
2020-12-16 05:37:12 +13:00

223 lines
6.3 KiB
Markdown

# math
Mathematical functions that generally only operate on a list of numbers (integers, decimals, bytes) and tables.
Currently the following functions are implemented:
* `math abs`: Returns absolute values of a list of numbers
* `math avg`: Finds the average of a list of numbers or tables
* `math ceil`: Applies the ceil function to a list of numbers
* [`math eval`](math-eval.md): Evaluates a list of math expressions into numbers
* `math floor`: Applies the floor function to a list of numbers
* `math max`: Finds the maximum within a list of numbers or tables
* `math median`: Finds the median of a list of numbers or tables
* `math min`: Finds the minimum within a list of numbers or tables
* `math mode`: Finds the most frequent element(s) within a list of numbers or tables
* `math round`: Applies the round function to a list of numbers
* `math stddev`: Finds the standard deviation of a list of numbers or tables
* `math sum`: Finds the sum of a list of numbers or tables
* `math product`: Finds the product of a list of numbers or tables
* `math variance`: Finds the variance of a list of numbers or tables
However, the mathematical functions like `min` and `max` are more permissive and also work on `Dates`.
## Examples
To get the average of the file sizes in a directory, simply pipe the size column from the ls command to the average command.
### List of Numbers (Integers, Decimals, Bytes)
```shell
> ls
# │ name │ type │ size │ modified
────┼────────────────────┼──────┼──────────┼─────────────
0 │ CODE_OF_CONDUCT.md │ File │ 3.4 KB │ 4 days ago
1 │ CONTRIBUTING.md │ File │ 1.3 KB │ 4 days ago
2 │ Cargo.lock │ File │ 106.3 KB │ 6 mins ago
3 │ Cargo.toml │ File │ 4.6 KB │ 3 days ago
4 │ LICENSE │ File │ 1.1 KB │ 4 days ago
5 │ Makefile.toml │ File │ 449 B │ 4 days ago
6 │ README.md │ File │ 16.0 KB │ 6 mins ago
7 │ TODO.md │ File │ 0 B │ 6 mins ago
8 │ assets │ Dir │ 128 B │ 4 days ago
9 │ build.rs │ File │ 78 B │ 4 days ago
10 │ crates │ Dir │ 672 B │ 3 days ago
11 │ debian │ Dir │ 352 B │ 4 days ago
12 │ docker │ Dir │ 288 B │ 4 days ago
13 │ docs │ Dir │ 160 B │ 4 days ago
14 │ features.toml │ File │ 632 B │ 4 days ago
15 │ images │ Dir │ 160 B │ 4 days ago
16 │ justfile │ File │ 234 B │ 3 days ago
17 │ rustfmt.toml │ File │ 16 B │ 4 days ago
18 │ src │ Dir │ 128 B │ 4 days ago
19 │ target │ Dir │ 192 B │ 8 hours ago
20 │ tests │ Dir │ 192 B │ 4 days ago
```
```shell
> ls | get size | math avg
───┬────────
# │
───┼────────
0 │ 7.2 KB
───┴────────
```
```shell
> ls | get size | math min
───┬─────
# │
───┼─────
00 B
───┴─────
```
```shell
> ls | get size | math max
───┬──────────
# │
───┼──────────
0 │ 113.6 KB
───┴──────────
```
```shell
> ls | get size | math median
───┬───────
# │
───┼───────
0320 B
───┴───────
```
```shell
> ls | get size | math sum
───┬──────────
# │
───┼──────────
0 │ 143.6 KB
───┴──────────
```
```shell
> echo [3 3 9 12 12 15] | math mode
───┬────
03
112
───┴────
```
```shell
> echo [2 3 3 4] | math product
72
```
```shell
> echo [1 4 6 10 50] | math stddev
18.1372
```
```shell
> echo [1 4 6 10 50] | math variance
328.96
```
```shell
> echo [1.5 2.3 -3.1] | math ceil
───┬────
02
13
2 │ -3
───┴────
```
```shell
> echo [1.5 2.3 -3.1] | math floor
───┬────
01
12
2 │ -4
───┴────
```
```shell
> echo [1.5 2.3 -3.1] | math round
───┬────
02
12
2 │ -3
───┴────
```
```shell
> echo [1 -2 -3.0] | math abs
───┬────────
01
12
2 │ 3.0000
───┴────────
```
### Dates
```shell
> ls | get modified | math min
2020-06-09 17:25:51.798743222 UTC
```
```shell
> ls | get modified | math max
2020-06-14 05:49:59.637449186 UT
```
### Operations on tables
```shell
> pwd | split row / | size
───┬───────┬───────┬───────┬────────────
# │ lines │ words │ chars │ bytes
───┼───────┼───────┼───────┼────────────
00155
1011111
2011111
30144
4021212
50177
───┴───────┴───────┴───────┴────────────
```
```shell
> pwd | split row / | size | math max
────────────┬────
lines │ 0
words │ 2
chars │ 12
bytes │ 12
────────────┴────
```
```shell
> pwd | split row / | size | math avg
────────────┬────────
lines │ 0.0000
words │ 1.1666
chars │ 8.3333
bytes │ 8.3333
────────────┴────────
```
To get the sum of the characters that make up your present working directory.
```shell
> pwd | split row / | size | get chars | math sum
50
```
## Errors
`math` functions are aggregation functions so empty lists are invalid
```shell
> echo [] | math avg
error: Error: Unexpected: Cannot perform aggregate math operation on empty data
```