Plotting with MATLAB plot command

With MATLAB, you can generate other types of plots, including contour and surfttce plots. You can also control the x- and y-axis scales. For example, the MATLAB s loglog (X, y) uses the base-10 logarithmic scales forx- andy-axes. Notexandy are the variables that you want to plot. The command loglog(X/y) is identical to the plot (x,y), ... 

NOTE If you do not define the color attributes, then by default MATLAB currently cycles through the colors blue, green, red, cyan, magenta, yellow, and black when creating multiple lines with a plot command, as shown in Fig. 1.16b. 

Let us now discuss the MATLAB commands that commonly are used when plotdi data. The plot (Xf y) command plots y values versus xvalues. You can use various line types, plot symbols, or colors with the command plot (x,y, s), where s is a charaaer string that defines a particular line type, plot symbol, or line color. The 8 can take on one of the properties shown in Table 15.12. 

Needless to say that within MATLAB we have all the algebraic, statistical functions predefined along with plotting capabilities. Before briefly commenting on the basics, it is interesting to point out the use of help within the command window. We use the help function followed by any built-in function and MATLAB returns a small tutorial on the use of that function, the arguments, and the options (i.e., try help ode45 ). 

From experimental data (file expdata.dat available on the worldwide web), we want to determine the best value of the product of the overall heat transfer coefficient times the heat transfer area (UA). You need to use the load command which will give you a two-dimensional array with time and temperature called exp-data. Is there a linear plot that allows for the use of linear regression MATLAB has the function polyfit that can perform this fit. What is the optimal vaue of UA for this system What do you think of the data MATLAB also has a function polyval that allows you to get best predicted values. 

MATLAB is a mathematical programme developed by the company called The MathWorks Inc. Examples in this chapter have been tested on MATLAB versions between 201 la and 2015b. It is expected that most of the commands presented will work with some earlier versions, as well as most later versions. It will be assumed that the reader has a basic understanding of MATLAB, can write MATLAB statements, understands basic MATLAB commands, and can plot a simple MATLAB graph. This chapter will examine in detail additional features, such as the different toolboxes and formatting features. In order to clearly distinguish between the code required for the MATLAB function and text, all MATLAB commands and variables are shown in bold Courier New. 

In this section the results of the measurements will be discussed. For the verification of the results a comparison model will be tacked. The comparison model is the transfer function of the low pass filter which is determined with the software tool Matlab. It will be execute measurements on the low pass filter and compared with result of the theoretical values. At firs the theoretical transfer function of the low pass filter will be plotted. This will be done over the following instruction on the command window of the Matlab tool. 

Alternatively, online help is available through the menu bar under Help. The question mark button on the tool bar will also invoke the Help Browser. Starting with 2008 releases, you can invoke a context-sensitive function browser, which lies on the left of the command prompt, and has the symbol f. You may type, for example, the command plot, and MATLAB will attempt to find all related MATLAB functions that include the word plot as part of their function names (Fig. 1.7). 

NOTE Notice here how MATLAB shows each command line within the M-file itself. Use echo off to suppress printing out each step, except for statements that do not end up with the suppressing symbol ( ), or for non-suppressible data and graph display (e.g., disp, plot, fplot, fprintf, etc.). 

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