ENG 1181 College of Engineering Engineering Education Innovation Center MatLab – 2D Plots 2 MATLAB has many built-in functions and commands to create various types of plots. 2D plot polar plot3D plot

ENG 1181 Two Dimensional Plots in MATLAB Topics Covered: Cautions when using different plot functions fplot polar plot histograms subplot

ENG THE fplot COMMAND fplot(‘function’,limits) The fplot command can be used to plot a function with the form: y = f(x)  The ‘function’ line can only contain one variable name, e.g. a=2;b=-1;c=3; fplot(‘ax^2+bx+c’, [-2,2]) will give an error message as a, b, and c will be considered variables  The function fplot produces a smooth plot of a function for a linear plot. Using fplot and then converting one or both axes to log axes will in general not produce a smooth plot, even when the plotted function should be smooth.

ENG 1181 THE polar COMMAND The polar command can be used to plot a function with coordinates r and Ɵ. polar(theta,r)  Theta and r should be equal length arrays, just as with the plot function.  Theta must be in radians.  The order of the variables is the opposite to the normal math order.  Hold on, hold off must be used to place multiple curves on the same graph.  The size of the graph (r coordinate scale) is set by the first curve plotted – so plot the largest curve first

ENG 1181 Histograms The hist command can be used to create a histogram, but produces a graph with connected columns which can look bad when printed in b/w. The graph can be improved by using hist to organize data and then feeding the results to the bar function which produces nicer results, e.g.  Step 1: Given an array y, [n, xout] = hist(y,nbins); will organize the values y into nbins equally spaced bins. The variable n is an array containing the number of occurrences in each bin and xout is an array containing the center location for each bin.  Step 2: bar(xout,n) will create a vertical bar chart of the data. The columns will be separated and look much better in b/w.

ENG THE subplot COMMAND subplot(n,m,locn) The subplot command can be used to organize a number of graphs in the same figure window  Subplot only indicates a location within the figure window to place a graph. The graph should be created following the subplot command. Any valid MATLAB plotting command may be used, e.g. plot, polar, semilogx, fplot, bar, stem, etc.  Not all locations in the array of graphs need to be used.  Within a figure window, the same values of n and m must be used for all subplot commands. Unfortunately subplot cannot be used as a sophisticated page layout tool. For example, you cannot place two figures at the top of a figure window with subplot(2,2,1) and subplot(2,2,2) and then place one figure at the bottom with subplot(2,1,2). Maybe someday this will work …