labmanual (1) - MIT OpenCourseWare http/ 2.672...

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MIT OpenCourseWare 2.672 Project Laboratory Spring 2009 For information about citing these materials or our Terms of Use, visit: .
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MATLAB FOR 2.672 This is a short introduction to the MATLAB software. The idea is to enable you to use MATLAB quickly. Refer to the MATLAB REFERENCE MANUAL for more sophisticated operations. TO USE MATLAB - click the MATLAB icon. It will set up your directory as default for you so that you can access your files. CONCEPTS o MATLAB is a giant calculator which remembers the values of all the variables you have calculated. - The command you type in is executed every time you hit a carriage return (CR). Use the up-and-down arrow keys to recall previous commands . - Sometimes you do not want the intermediate results to be printed (e.g., when you are calculating the values of a thousand numbers). To do this, end the command with semi-colon, before the CR. - For a very long command that you cannot finish in one line, the line can be continued to the next by using the ellipsis consisting of three dots. .. , before the CR. o One can store a set of commands in a script file and recall it to be used. More of this later in the section SCRIPT FILES . (Using a script file is preferred if you have to do any serious calculations because then you have a record of all the commands you put in, and you can edit them and redo the command sequence easily.) o If you want to clear your "calculator," use the command CLEAR . You can clear a specific variable by CLEAR variable_name . o Variables in MATLAB are case sensitive!!! If you prefer, you could adapt the convention of using lower- case characters for scalars and upper-case characters for vectors and matrices. o MATLAB stands for MATRIX LABORATORY; therefore, the basic representation of information is in terms of matrices. A number, or scalar, is a 1x1 matrix. In 2.672, we mostly deal with vectors (e.g., an array of data). Because the software is matrix-based, there can be quite a bit of confusion if you are not careful. For example, if x is a 5x1 matrix (i.e., a column vector of 5 elements), X*X is illegal. On the other hand X*X' ( X' stands for the transpose of X) will give you a scalar. o You can always click the HELP icon to search for information within MATLAB. BASIC OPERATIONS o The operators +,-,*,/,^ have the usual meaning. (The last one is to raise power.) - operation between a scalar (s) and a matrix (A) is straight forward; e.g. s*A means that every element of A is multiply by s. - For operations between matrices (vectors are special case of matrices: a row vector of n elements is a nx1 matrix; a column vector is a 1xn matrix), you have to be careful that the dimensions match, or you will get error messages. - Division means multiplication by the inverse matrix. As such, there are two different symbols: the right
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labmanual (1) - MIT OpenCourseWare http/ 2.672...

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