Gnuplot/C2/Plotting-functions/English
| Visual Cue | Narration |
| Slide Number 1
Title Slide Plotting functions |
Welcome to the tutorial on Plotting functions in gnuplot. |
| Slide Number 2
Learning Objectives |
In this tutorial we will learn,
|
| Slide Number 3
Learning Objectives |
and
|
| Slide Number 3
System and Software Requirement |
To record this tutorial, I am using
and
|
| Slide Number 4
Pre-requisites |
To follow this tutorial,
|
| Press Ctrl Alt T . | Open a terminal by pressing Ctrl, Alt and T keys simultaneously. |
| Type cd Desktop and press Enter. | A terminal opens.
Change directory to Desktop as seen. |
| Type gnuplot and press Enter. | In the terminal, type gnuplot and press Enter. |
| Hover mouse near gnuplot prompt. | The prompt changes to gnuplot prompt.
To execute a command in the terminal, press Enter after typing it. I will not mention this separately. |
| Press Ctrl shift K. | I will clear the terminal. |
| Type plot sin (x) and Press Enter. | Now type plot space sin (x).
Note that angle x is within parentheses. |
| Point to graphical window. | A graphical window with plot of sin(x) versus x appears on the screen. |
| Hover mouse on graph, axes. | The limit of the Y axis is from minus 1 to plus 1.
And the X axis is from -10 to 10. |
| Type set grid and press Enter. | Come back to the terminal and type the command set space grid. |
| Type replot and press Enter | Then type replot to see the grid in the graph. |
| Hold Ctrl and zoom in with mouse scroll. | Hold down the Control key and move the mouse scroll wheel to zoom in and zoom out. |
| Point to sin x and x. | Observe that sin x is zero when x is zero. |
| Show zoom in and out. | Let us reset the limits of the axes as before. |
| Type reset and press Enter. | To reset, type the command reset in the terminal, followed by replot. |
| Type replot and press Enter. | Changes in the graph become visible only after executing the replot command. |
| Point to the legend. | Notice that the legend is on the top right side in the graph.
It is not clear and intersects the graph. |
| Point mouse on the legend. | Let's increase y axis range, so that the graph line does not intersect the legend. |
| Type set yrange [-2:2] and
press Enter. |
Type set space yrange space -2 colon 2 within square brackets. |
| Type set xrange [-20:20] and
Press Enter. |
I will also change x axis range.
Enter command, set space xrange space -20 colon 20 within square brackets. |
| Type replot and
Press Enter |
Type replot to see the updated graph. |
| Now the changed graph limits are visible. | |
| Point to the legend. | The legend has moved up and does not intersect the data line anymore. |
| Type set key top left and press Enter | Type set space key space top space left to move the legend to the top left side. |
| Type replot and press Enter. | Do not forget to replot to see the result. |
| Hover mouse next to axis font. | Next, let's make the axes fonts larger.
I want to set them at size 14 and in Verdana style. |
| Type set tics font “Verdana, 14” and press Enter. | Type this command as shown here, to change the font size and style.
Replot to see the result. |
| Hover mouse next to axis font. | Notice the larger font size in Verdana style. |
| Type set xlabel 'x (angle)' font “Verdana, 14”.
Press Enter |
Let's set x axis label as x angle.
Type the command as shown here. Here we are specifying the label, font style and size in a single command. |
| Type set ylabel 'sin (x)' font “Verdana, 14” and press Enter. | To set y axis label as sin x, type the command, as shown here. |
| Only narration. | We are using the same font size and style for y axis too. |
| Type replot and
Press Enter |
Type replot and press Enter. |
| Only narration | Now, let’s see how to change the font in the legend. |
| Type set key font ",16" and
Press Enter |
Type
set space key space font space within double quotes comma 16 . This command sets the legend font size to 16. |
| Press Ctrl+Alt+K. | I will clear the terminal. |
| Type help fonts and
Press Enter |
To access help documentation on fonts, type help space fonts. |
| Point mouse to cairo, gd and postscript | Help command returns with 3 subtopics cairo, gd and postscript. |
| Type cairo and
Press Enter |
I will type cairo to see the details and available options. |
| Only narration | Similarly you may choose to use help for any command when using gnuplot. |
| Mouse in Help section. | You may pause the video and read the details given in the help section. |
| Press Ctrl C | Once done, press Control and C keys to exit the help section. |
| Ctrl+L in Ubuntu and
Ctrl+Shift+K in Debian. |
I will clear the screen.
I wish to add a title to my graph. |
| Type set title 'My first gnuplot' and press Enter. | To add a title, type set title command, as shown here.
Followed by the title of the graph in single quotes. |
| Type set title font "verdana, 18" and press Enter. | To set the title font, type the command as shown here. |
| Point to x axis. | In the sinx versus x plot, dimensions of x axis is angle.
Hence we may want to label X axis in terms of angle, π. |
| In the terminal, type,
set xtics ('-4{/Symbol p}' -4*pi,'-3{/Symbol p}' -3*pi,'-2{/Symbol p}' -2*pi, '-{/Symbol p}' -pi, 0, '{/Symbol p}' pi,'2{/Symbol p}' 2*pi, '3{/Symbol p}' 3*pi, '4{/Symbol p}' 4*pi,) and pressEnter. |
To change X ticks to angle, type the following command as shown on the screen.
Here we are using the Greek alphabet pi and setting its position. |
| Point mouse to ('2{/Symbol p}' and then to 2*pi. | This command places, Greek symbol pi, at the value of 3.14.
Label 2π is at position 6.28 on the X axis. |
| Point to 2π and 4π. | Multiples of pi are placed at their respective positions. |
| Type help set xtics
Press Enter |
For more help on the formats of X tics, type the command help space set space xtics. |
| Press Ctrl C. | Press Ctrl and C keys to exit the help section. |
| Press Ctrl+Shift+K in Debian. | I will clear the terminal. |
| Only narration | It is also possible to add multiple functions on the same graph. |
| Type plot sin (x), cos (x) and press Enter. | To plot sin x and cos x on the same graph, separate the functions by a comma.
Type plot space sin x comma cos x Make sure that the angle x, is within parentheses . |
| Point to the graph window. | Notice that the two functions are plotted together now. |
| Only narration. | Next, we will add sin (x) plus cos (x) function to the same graph. |
| Type plot sin(x), cos(x), sin(x) + cos(x) and press Enter. | For this, type plot space sin(x) comma cos(x) comma sin(x) plus cos(x) . |
| Point to the graph window. | Notice that all 3 functions are plotted together on the same graph now.
Next, let’s learn how to get sin(x) data points into a file. |
| Only narration. | To get an ASCII column format output, set table command can be used. |
| Type set space table and press Enter. | First type set space table. |
| Enter command plot sin(x) and press Enter. | Then type plot space sin(x). |
| Point to the screen | An x y column data for sin(x) is generated on the screen. |
| Highlight first column.
Highlight second column. |
The first column is x data and the second column is y data.
They are the points of sin x versus x graph. |
| Press Ctrl+Alt+K | I will clear the terminal.
We can save the output as a text file. |
| Type set table "table-sinx.txt" and press Enter | For this, type set space table space within double quotes sinx dot txt.
Here sinx dot txt is the output filename. |
| Type plot sin(x) and press Enter. | Then, type plot space sin(x).
The output is saved to the file sin x dot txt. The data is not seen on the screen. |
| Show screenshot of Desktop showing the file sinx.txt. | The file is stored in the directory from where we opened gnuplot in the terminal. |
| Type unset table and press Enter. | Type unset space table to exit the tabular output mode. |
| Enter q | Then type quit or q to quit gnuplot. |
| Slide Number 6
Summary |
Let’s summarize.
In this tutorial, we plotted 2D graphs of functions. We also
and
|
| Slide Number 7
Assignment |
As an assignment, plot the following functions:
|
| Completed assignment | Your completed assignment should look like this. |
| Slide Number 8
Spoken Tutorial Project |
This video summarises the Spoken Tutorial Project
Please download and watch it. |
| Slide Number 9
Spoken Tutorial workshops |
We conduct workshops using spoken tutorials and give certificates.
Please write to us. |
| Slide Number 10
Forum for specific questions: |
Post your timed queries in the forum. |
| Slide Number 11
AcknowledgemenT |
Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. |
| This is Rani from IIT, Bombay. Thank you for joining. |
