In this example we plot a sin wave,
 
The first example just plots one sinusoid.
Run it using load 'gnu.wave' from within gnuplot.  
The next example plots two sinusoids and
their sum.
load 'gnu.wave2'  
The next example shows how to make a movie
by using load 'gnu.wave4' to recursively carry out
functions that increment t and replot.
You should run this command 
load 'gnu.wave3'  
 noting that that file loads this one, which
then loads itself again...
It loads itself forever, so you will need to hit CtrlC to stop it. [Some windowmanagers have the annoying feature that by default whenever a fresh plot happens in gnuplot, the window manager gives focus to the gnuplot window; this default behaviour can be disabled. I like to have focus follow the mouse.]  
The next example rectifies the problem of the neverending movie by
loading gnu.wave6 which contains an if
before its load command.
Run this example using
load 'gnu.wave5' 

This file, gnu.wave6, is used by all the remaining examples.  
You'll probably find that the previous example, gnu.wave5, which increased the xrange of the plot, produced a pretty lousylooking plot, which didn't look like pictures of sinusoids any more. The problem was that the sinusoid has too many wiggles compared with the default number of samples. We fix this problem by cranking up the number of samples. This file, gnu.wave7, shows how.  
In these files, gnu.wave8 and gnu.wave9, we play around with the value of w2 a little, seeing the effect of changing the dispersion relation. 

This file, gnu.wave10, goes the whole hog, adding up five sinusoids. Physicists may find it instructive to play with the definition of the parameter dwdk.  
gnuplot has a function called fit
which can fit parameterized functions to data files
by twiddling whichever parameters you choose.
The objective function that is minimized by the fitting process is the sum of squares of residuals. [The residuals are the differences between the functions and the data points.] This is the standard objective function, widely used in datafitting, but do be careful to think whether it is an appropriate objective function. It's appropriate, for example, if you wish to model the residuals as coming independently and identically distributed from a gaussian distribution. fit is a pretty neat function. Its syntax is similar to the plot syntax. For this section, there are two data fails necessary to run the examples: 2006/Year and 2006/YearTd.  
This first file, gnu.fit1, simply plots two data files,
one of which contains halfhourly temperature data, and one daily
averages of temperatures. It also plots a function
plot '2006/Year' u ($0/48.0):($2) w l lt 6 ,\ '2006/YearTd' u ($10.5):($2) w l lt 8,\ f(x)


The second file, gnu.fit2, plots the data files and f(x)
as before, then runs the function
fit f(x) '2006/YearTd' u ($10.5):2 via A,o,Bso as to fit the function f(x) to the average daily data. Note that the syntax of the "u" (using) part is the same as used in the plot. The words via A,o,B instruct the fit function to vary those three parameters so as to optimize the fit of the function f(x) to the specified data. If all is well, this fit function will come up with a good setting of the parameters, report them with error bars and a correlation matrix, the stop; the next command in the gnuplot file replots the function so you can see how it fits.  
gnu.fit3 fits a more complicated model to the halfhourly data  the temperature is modelled as the sum of two sinusoids, one with period one day, and one (as before) with period one year. Here the plot of the function is a fancy 'multiplot' with three parts. To avoid writing everything twice, the details of the plot command are popped into another file, gnu.showTempg, which is loaded whenever we want to make the threepart plot.  
gnu.fit4 shows off fit's capabilities by fitting a more complicated model, in which the daily sinusoid has an amplitude that itself varies sinusoidally with a period of one year. To find out more about fit, use ?fit  
If you have a load of points in datafiles and
want to make a movie, there are two ways
with gnuplot.
plot 'datafile' every 10 using 3:5which plots every 10th line in 'datafile', showing column 3 on the x axis and 5 on the y axis. Use ?every to find out the fancier things you can do with every Note that gnuplot calls the top line of a file line zero, not line one. The example shown here [run it using load 'gnuC02' ] shows a spaceman and his hammer orbitting the earth. The spaceman is in circular orbit. The spaceman has just given his hammer a kick directly away from the earth. 

There are several ways to make histograms.
For example, you could pop your data into a spreadsheet
and use its builtin histogram function.
However there is a sneaky way to do the histogram entirely
within gnuplot.
To adapt this trick to your problem, change the datafile 'dat' to your data file; change the $1 to point to the correct column number (eg, $2 for column 2); choose the bin_width you want. This example assumes the data is in a file called dat. 