# Preceding an operator with a period indicates an

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Unformatted text preview: an operator with a period . indicates an array or element-by-element operation. For example, if X = 1 2 3] and Y = 4 5 6] then X: Y = 4 10 18]. Notice that the usual vector product X Y is unde ned. The Matlab object ones(m,n) is useful if you want to add or subtract a constant from each element in a vector. ones(m,n) is an m-by-n matrix of ones. Using the vector X from the last example, you write the expression X + 2 as follows in Matlab notation. X + 2 * ones(1,3) The dimension of ones vector must match the other vectors in the computation. The command size(A) returns the dimension of a vector or matrix A. On-line Help Matlab has on-line help for all its commands. For example, try any of these commands: help print help help help general Making Plots Matlab provides a variety of functions for displaying data as 2-D or 3-D graphics. For 2-D graphics, the basic command is: plot(x1, y1, 'line style', x2, y2, 'line style'...) 2 This command plots vector x1 versus vector y1, vector x2 versus vector y2, etc. on the same graph. Other commands for 2-D graphics are: polar, bar, stairs, loglog, semilogx, and semilogy. For 3-D graphics, the most commonly used commands are: plot3(x1, y1, z1, 'line style', x2, y2, z2, 'line style'...) contour(x,y,Z) mesh(x,y,Z), surf(x,y,Z) The rst statement is a three-dimensional analogue of plot() and plots lines and points in 3-D. The second statement produces contour plots of the matrix Z using vectors x and y to control the scaling on the x- and y- axes. For surface or mesh plots, you use the third statement where x, y are vectors or matrices and Z is a matrix. Other commands available for 3-D graphics are: pcolor, image, contour3, ll3, cylinder, and sphere. Example 1: Plot y...
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