#compsci #physics #software 

Gnuplot is a command-line program that can generate 2- and 3- dimensional plots of [[Числовая функция|functions]], data, and data fits.

## Syntax
[[Python core data types summary|Python]]-esque syntax:
```gnuplot
f(x)=sin(x)
plot f(x)
```

### Arrays
```gnuplot
array A[6]
A[1]=1
A[2]=2.0
A[3]={3.0, 3.0}
A[4]="four"
A[6]=A[2]**3
do for [i=1:6] { print A[i], B[i]}
```
Result:
```gnuplot
1
2.0
{3.0, 3.0}
four
<undefined>
8.0
```
(as seen here, gnuplot supports [[iteration]] and block-structured if/else/while/do constructs)

Array indices run from 1 to N for an array with N elements.
Element i of array A is accessed by A[i].

Function index(Array, %value%) returns an intenger i such that A[i] is equal to %value%. Return of 0 indicates that no match was found
![[Pasted image 20241007213921.png]]

### Setting output
Output defined by **set term %value%**
For list of values, use **set terminal**
Common values:
qt
windows (on [[Windows]])
png
pdf
pm3d (for 3dimensional graphs) (**set pm3d**, not set term)

Setting fonts:
```gnuplot
set term png font "arial"
set term png font "/usr/loca/fonts/ttf/arial.ttf"
```

Setting font size:
```gnuplot
set term png tiny/small/medium/large/giant
```

Setting output file:
```gnuplot
set output "filename"
```

For tables:
```gnuplot
set table "output.dat"
replot
unset table
```
### Linetype and linecolor
```gnuplot
plot sin(x) linetype %value%
```
for different line types/colours
where %value% is a number

```gnuplot
plot sin(x) linecolor rgb "#FF00FF"
plot sin(x) lc rgb "#FF00FF"
```

Most terminals allow you to set an explicit background color:
```gnuplot
set term png background rgb "gray75"
```

### Linewidth
```gnuplot
plot sin(x) linewidth 5
```

### Dashtype
The dash pattern is a separate property associated with each line:
```gnuplot
plot f(x) dashtype %value%
```

where %value% is a number

### Strings
Title:

```gnuplot
plot 'data.4' title "Title for plot 4"
```

```gnuplot
set title "Graph something" offset -10 font "Arial, 20" textcolor "red"
```

Axes labels:
```gnuplot
set xlabel "This is x" font "Helvetica, 14"
set ylabel "This is y" font "Helvetica, 14"
```

Marks on axes:
```gnuplot
set xtics 0, pi/2 // step pi/2 with starting point 0
```
Logarithmic scale:

```gnuplot
set logscale xy 10
```
### Plotting styles
Gnuplot supports many plotting styles:
- **boxes**
- **lines**
- **arrows**
- **vectors**
- **candlesticks**
- **circles**
- **dots**
- **points**

And other, for more information consult the documentation.

For points:
```gnuplot
plot sin(x) with points pt 12 ps 1.5
```
where pt = pointtype (value means symbol name), ps = pointsize
### Commands
#### cd
Change directory
```gnuplot
cd '%directory-name'
```

#### fit
Fits a user-supplied real-valued expression to a set of data points, using the [[Regression line|least squares]] algorithm.

![[Pasted image 20241007221929.png]]
![[Pasted image 20241007233238.png]]
#### plot
Main command.
Modes:
**set polar** (unset polar)
**set parametric** (![[Pasted image 20241007224004.png]])

For 3D plots:
```gnuplot
set pm3d
splot ...
```
#### Other
Other commands include if, for, print, pwd, quit, reset, etc.

### Ranges
```gnuplot
set xrange [0:12]
set yrange [0:3]
```

### Multiplot mode
Multiplot mode allows for the plotting of several graphs in one image
```gnuplot
set multiplot
set size 0.5, 0.5 // relative size
set origin 0., 0. // relative origin
plot sin(x)
set size 0.5, 0.5
set origin 0.5, 0.5
plot cos(x)
unset multiplot
set size 1., 1. // resetting size
set origin 0., 0. // resetting origin
```

![[Pasted image 20241007230145.png]]

### Data manipulation
Say you have a file "data.dat" with 2 columns and you want to multiple the values in the first column by 2:
```gnuplot
plot 'data.dat' using ($1*2):2 with points
```

### Histograms
```gnuplot
bin_width=0.1 // select bin width
set boxwidth 0.9*bin_width absolute // histogram style
set style fill solid 1 noborder // style
bin_number(x)=floor(x/bin_width) // box distribution
rounded(x)=bin_width*(bin_number(x)+0.5) // box middle coord
plot 'data.dat' using (rounded($2)):(1) smooth frequency with boxes
```
![[Pasted image 20241007232656.png]]