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--- supp:octave:contrib:surface_plot:start [2016/04/14 09:09] – created admin
+++ supp:octave:contrib:surface_plot:start [2016/04/14 09:12] (current) – [Partial Solution] admin
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 ====== Octave: Surface, Contour (Isolines), Gradient ======
+===== Functions of Two Variables =====
+{{:phy2:ss2013:surf.jpg?direct&300|}}
+In Octave analyse the function f(x,y) = x^2*y - 2*y.
+  * Understand what a meshgrid is, how it is generated and how it is used.\\ Define x=[-2:0.1:2]; and y=[-1:0.1:1]; and generate the meshgrid yielding X and Y.
+  * Define Z=(X.^2).*Y-2*Y; . Z is the matrix containing the function f evaluated at all points of the meshgrid.\\ Generate a surface plot in the first figure window.
+  * Generate a contour plot in the second figure window.
+  * Use the function [dX,dY] = gradient(Z); to estimate the gradient of f at each point of the meshgrid.
+  * Open a third figure window. Add a contour plot, hold the plot, and add a vector arrow plot (octave buit-in function quiver).\\ How are contour lines and gradient vectors related?
+==== Solution ====
 Download the script by klicking on the file name in the box header. Execute the file in Octave. Compare the results with the gradients determined in the lecture.