GNUPLOT

- not so Frequently Asked Questions -

update 2004/8/31

Introduction to gnuplot --- Plot Style

Here you can see what kinds of graph gnuplot can draw. To specify the style of graph, with style . To connect the data points with lines, use with lines . The with points option places symbols at the data points.

Those styles can be easily combined. For example, to draw a line graph and a bar graph at the same time:

gnuplot> plot "file.dat" with boxes, "" notitle with lines
up

Draw Lines, Dots, and Symbols

lines

It connects each data point with lines. Suitable to smoothly varying data.

style1.png
dots

It displays dots, can be used when there many data points, but hard to see though.

style2.png
points

Symbols are shown at the data point location, can be used to plot experimental data. The number of different kinds of symbol depends on your terminal, but there are at least 6. The number '-1' is a dot. The size of symbol can be changed by the set pointsize command.

style3.png
linespoints
lp

Draw lines and symbols at the same time.

style4.png
impulses

Draw vertical lines from each data point to X-axis. This is a bar-graph without width.

style5.png
steps
fsteps
histeps

Three kinds of histgram. The difference of those is a definition of starting and ending points, which you can see below. Gnuplot can draw a histgram, but it cannot calculate the histgram data themselves.

style6.png

Here you can see the difference of 3 histgrams.

The data position is shown by a blue box. With steps , the data point defines an initial position, while the data points are treated as the final position with fsteps . With histeps a graph becomes a kind of bar-graph but the bars stick together.

steps
style6a.png
fsteps
style6b.png
histeps
style6c.png
up

Draw a Bar-Graph

boxes

This bar graph resembles the histgrams above except for vertical lines. Inside the each bar is empty, cannot be filled with color. If you want a color-filled bar-graph, exports the produced graph into some drawing softwares line Tgif, and paint them.

style7.png

A width of each bar is calculated automatically so that each box touches the adjucent box. To control the width, use set boxwidth width. For this case the width of all boxes become width . The width can be given by a data file, the third column (otherwise you can specify the column by using X:Y:Z where Z becomes the width). In the example below, the data points are shown by blue symbols

default

Widths are calculated automatically

style7a.png
set boxwidth 1

Set the width to 1

style7b.png
data file

When your data file has the third column, that is used for the bar-width. In the right figure, widths of 1,2,1,2... are given in the file

style7c.png
up

Draw Symbols with Error Bars

yerrorbars

Same as 'points' but Y values have errors. The length of error bar is given in a file. If the data file has 3 columns, the third column is used as the Y-error, Y plus/minus dY. It there are 4 columns, the third and fourth columns are used, likel, Y plus dY1 minus dY2.

style8a.png
xerrorbars

Same as 'yerrorbars' but the error bars are horizontal.

style8b.png
xyerrorbars

Both X and Y values have errors. You need 4 or 6 columns data.

style8c.png

See data file how to specify the data and data errors.

vector

Draw vectors. An arrow is plotted from (X,Y) to (X+dX,Y+dY). So that you need 4 columns data in your data file.

style9.png

There are two styles those can be used for financial plot. Those were categorized into "others" here, because the author of this page is not good at finance :-) Maybe those are used for plotting of variation of stok or price. The style "financebars" and "candlesticks" requires 5 columns which are date/time, opening, low, high, and closing prices, respectively.

financebars

High and low prices are connected with a vertical line, and opening and closing prices are indicated by small horizontal tics. The length of the tics can be changed by set bar.

style10.png
candlesticks

Similar to "financebars". A rectangular represents opening and closing prices, and a horizontal line segment shows high and low prices.

style11.png
up