Gnuplot plot text file

To specify the columns to be plotted use the using specifier. In the case your data set is a tridimensional file just use splot ad add the z-column. There are also different style see gnuplot documentation or Selecting a plotting style for further infos for plotting points. As said before, the default style is point. In the case you have more columns and want to plot them all in the same graph just pass to the plot function any argument you prefer, by separating them with a , :.

Here is an example:. These changes do not have an effect until you redraw the plot. This can be done by typing in the plot command again, but if the plot itself does not change, it is enough to type:. It's often nice to add a grid to the plot, making it easier to see where functions and data fall on the plot.

To do this, type. After learning how to plot functions, now it's time to learn how to plot data. The syntax is almost the same, except that instead of specifying a function, you must specify the name of the file containing the data to plot, enclosed in double quotes. First, since we were playing around with plots above, we'll clear the labels on the axes and other settings:. You could also quit gnuplot and restart it for the same effect. Now, we'll plot our sample data.

We'll get rid of an entry in the legend for our data points by using a title of "" , and also set up the axes on the plot:. When plotting data, it usually isn't necessary to specify ranges for the independent and dependent variables, since they can be figured out from the input. If necessary, of course, you can always give them. Since our input data contains uncertainties for the measured dependent quantity, we can create y error bars.

Once again, gnuplot makes this easy:. It's possible to plot x error bars using xerrorbars , or both x and y errorbars using xyerrorbars. When both x and y error bars are used, there must be four columns present, and x error bars must be specified first in the data file.

More variations are possible; see the online help for more information. Note that gnuplot can be very picky about the order you give modifiers to the plots. If you were instead to type. You'd get a rather strange error message: undefined variable: title. If you see error messages like this, check the ordering in your plot commands.

If you're unsure, typing help plot should get you straightened out. No plotting program would be complete without the ability to fit our data to a curve. For the Cavendish experiment, we'll need to fit our data to a sinusoidal curve with exponential decay. First, it's necessary to define the form of the function we'll try to fit to. Define this as you would any other function in gnuplot, but leave variables for the fitting parameters.

We'll use. For a non-linear curve fit such as this, it is often necessary to provide an initial guess for each of the fitting parameters, or the fitting attempt may fail. For simple equations, such as polynomials, this will not be necessary but never hurts.

Here's how the command is interpreted: fit tells gnuplot we're doing a curve fit. The next part, theta x , must be a function that we're using to fit the data. Here we must use x as the independent variable. The next part, "cavendish. The using tells gnuplot to take columns 1, 2, and 3 from the data file and use them as the x, y, and uncertainties, respectively. If this part is left out, then the experimental uncertainties will not be used for the curve fit.

See below for a greater discussion of the extremely powerful using qualifier. Finally, we must tell gnuplot what variables it can adjust to get a better fit. For this case, we say via a, tau, phi, T, theta0. Important quantities to note are the reduced chi square variance of residuals , which in this case is 1. Each fitting parameter also has an uncertainty listed. The correlation matrix at the end can ususually be ignored. All values start, stop and increment are casted to integer values.

The simplest method to plot multiple data files is to insert a for loop inside the plot command of gnuplot. Assuming you have N files named sequently, i. Another possible path to follow is using the sprintf function that works basically the same as the C-language sprintf.

The right syntax, from the gnuplot 5. Gnuplot Basic plotting of data files. Introduction One of the main useful features of gnuplot is the possibility of plotting data files.