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Plotting 2 functions in matlab how to#

% IMPLICITPLOT3D(eq, val, xvar, yvar, zvar, xmin, xmax, For this one can use the following M-file implicitplot3d: A plot showing more than one contour is usually difficult to interpret, so we willĭiscuss plotting a single contour. This can be viewed as a threeĭimensional version of contour plotting. MATLAB's capabilities, but we can draw a picture of a single level surface of the function. The graph of a function of three variables would require a four dimensional plot, which is beyond This is analogous to parameterizing a curve and writing x, y, and z each as a function of t.

(2) We can parameterize the surface by writing x, y, and z each as functions of two parameters, say s and t.

(1) We can write the surface as a level surface f(x, y, z) = c of a function of three variables, f(x, y, z).

Obtain surface mesh and line plots of the function We could have also used the ez plotting functions, as in: Of the parameter grid, and the plotting function to be used. The essential information for such a plot is the name of the symbolic vector that defined the parametrization, the specification Zfun can now proceed with the plot in any of several ways: surf(X1,Y1,Z1)īy now, it may have occurred to you that we could have issued exactly the same sequence of commands for any parametrized surface. Then we evaluate this function at each point of the grid, to define the array of z-coordinates for the plot. The output of vectorize is a string, so we use eval to evaluate it as a function. Next, we must make f from a symbolic expression into a vectorized function, since it must operate on our arrays of x- and y-values. Note the use of the semicolon! If we had not suppressed the output, MATLAB The command creates a grid with both the x and y coordinates varying in steps of. We use X1 and Y1, rather than x and y, because we want to reserve the latter for symbolic variables. We start by defining the coordinate grid with the meshgrid command. In this case, the parameters are also the x and y coordinates. We will illustrate how this works to plot the graph of the function f above. Thus for aĬurve, the arguments are usually linear arrays, or vectors, while for a surface, they are rectangular arrays, or matrices. The entries give the coordinates as functions of the parameters (which may be identical with the coordinates). The positions in these arrays correspond to parameter or coordinate values The arguments to a MATLAB plotting function, suchĪs surf, plot, plot3, mesh, or contour, are two or three identically shaped arrays.

We begin with a brief discussion of how MATLAB does its plotting. Values of the function, and red denoting the largest. Note that MATLAB again color-codes the output, with blue denoting the smallest

Two variables is a surface, but not conversely. Graph is a surface, in other words, a two-dimensional geometric object sitting in three-space. Once you execute this command, you can rotate the figure in space to be able to view it from different angles.

Plotting 2 functions in matlab how to#

We will see later why this is so and how to detect it.īut for the time being let's move on.

One of the pictures in this case is misleading the contour in dark blue in the very middle should really have

The color coding in the contour plot tells us how the values of the constant c are varying. All we need as arguments to ezcontour are the expression, whose contours are to be plotted, and the ranges of values for x and y. (In other words, it is not necessary to use an M-file or an anonymousįunction as an input to the plotting command.)į=((x^2-1)+(y^2-4)+(x^2-1)*(y^2-4))/(x^2+y^2+1)^2 Note that our plotting commands can take as input an expression that defines a function, rather than a function itself. We will take f sufficiently complicated to be of some interest. We begin by illustrating how to produce these two kinds of pictures in MATLAB, using MATLAB's easy-to-use plotting commands,Įzcontour and ezsurf. the graph of the function, which is the set of points (x, y, z) in three-dimensional space satisfying f(x, y) = z.a contour plot, or a two-dimensional picture of the level curves of the surface, which have equations of the form f(x, y) = c, where c is a constant.