Lecture note Data visualization - Chapter 20

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This chapter presents the following content: Graphic window, edit window, start button, matrices in matlab, scalar operations, order of operations, array operations, matrix addition, matrix multiplication, number display (scientific notation), script m-files.

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Nội dung Text: Lecture note Data visualization - Chapter 20

Lecture 20
Recap Graphic Window Edit Window Start Button Matrices in MATLAB Scalar Operations Order of Operations Array Operations Matrix Addition
Types of Mfiles Two types Script Function
Script Mfile The script can use any variables that have been defined in the workspace, and any variables created in the script are added to the workspace when the script executes A script created in the MATLAB edit window can be executed by selecting the Save and Run icon from the menu bar A script can be executed by typing a file name or by using the run command from the command window No matter how you do it, you can only run an Mfile if it is in the current folder
Editor/Debugger Window
Cell Mode It is a utility that allows the user to divide Mfiles into sections, or cells, that can be executed one at a time This feature is particularly useful as develop MATLAB ® programs are developed To activate the cell mode, select Cell > Enable Cell Mode from the menu bar in the edit window Once the cell mode has been enabled, the cell toolbar appears
It’s important to include the space after the double Continued…. percentage sign (%%). If don’t, the line is recognized as a comment, not a cell divider Once the cell dividers are in place, if cursor is positioned anywhere inside the cell, the entire cell turns pale yellow Now use the evaluation icons on the cell toolbar to evaluate a single section, evaluate the current section and move on to the next section, or evaluate the entire file Also on the cell toolbar is an icon that lists all the cell titles in the Mfile
Continued…. By dividing the program into cells, it was possible to work on each problem separately Be sure to save any Mfiles developed this way by selecting Save or Save As from the file menu: File > Save or File > Save As The reason for using these commands is that in cell mode, the program is not automatically saved every time when it is run
Summary of Chapter
Chapter 3 Built in MATLAB Function
Using Builtin Functions Many of the names for MATLAB’s builtin functions are the same as those defined not only in the C programming language, but in Fortran and Java as well For example: to take the square root of the variable x , we type b = sqrt(x) A big advantage of MATLAB is that function arguments can generally be either scalars or matrices In our example, if x is a scalar, a scalar result is returned Thus, the statement
Continued…. However, the squareroot function, sqrt , can also accept matrices as input In this case, the square root of each element is calculated, so x = [4, 9, 16]; b = sqrt(x) returns b = 2 3 4 All functions can be thought of as having three
Continued…. Some functions require multiple inputs For example: the remainder function, rem , requires two inputs: a dividend and a divisor. We represent this as rem(x,y), so rem(10,3) calculates the remainder of 10 divided by 3: ans = 1 The size function is an example of a function that returns two outputs, which are stored in a single array. It determines the number of rows and columns in a matrix.
Continued…. A useful feature of the more recent versions of MATLAB is the adaptive help capability As a function name is typed, a screen tip appears showing the correct function format It also includes a link to the function’s help page. A more complicated expressions can be created by nesting functions For instance: g = sqrt(sin(x))
Using the HELP Feature MATLAB includes extensive help tools, which are especially useful in understanding how to use functions There are two ways to get help from within MATLAB A commandline help function An HTMLbased set of documentation available by selecting Help from the menu bar, selecting the help icon or by using the F1 function key There is also an online help set of documentation, available through the Start button or the Help icon on the menu bar
Continued…. To use the commandline help function, type help in the command window help A list of help topics will appear: HELP topics: MATLAB\general – Generalpurpose commands MATLAB\ops – Operators and special characters MATLAB\lang – Programming language constructs MATLAB\elmat – Elementary matrices and matrix
Example to get help on the tangent function, type help tan The following should be displayed: TAN Tangent of argument in radians. TAN(X) is the tangent of the elements of X See also atan, tand, atan2