Student Support Forum: 'Plotting and defining functions' topicStudent Support Forum > General > Archives > "Plotting and defining functions"

 Next Comment > Help | Reply To Topic
 Author Comment/Response Rayne 01/27/07 01:18am Hi all, I want to plot the cubic equation f(x) = x^3 - 16x^2 + 3x + 1 = 0. I had: f=x^3-16 x^2+3 x+1 == 0 Plot[f,{x,-1,20}] but I was unable to get the plot. The error message says Plot::plnr: f is not a machine-size real number at x = -0.999999. Plot::plnr: f is not a machine-size real number at x = -0.148093. Plot::plnr: f is not a machine-size real number at x = 0.780985. General::stop: Further output of Plot::plnr will be suppressed during this calculation. How do I get around this problem? Also, I need to define a set of functions for vector calculus. Two of them are the gradient (equivalent to Del[f] in Mathematica) and the laplacian (equivalent to [CapitalDelta]). I have: gradient[f_]:={D[f,x],D[f,y],D[f,z]} and laplacian[f_]:=D[f,{x,2}]+D[f,{y,2}]+D[f,{z,2}] As you can see, this only works if the function f has 3 variables. How do I make it more general, that is, for an arbitrary number of variables? Also, how do I use the Del and CapitalDel functions in Mathematica? I tried Del[f] when f is 2x^3-3y^2+4z and only got \[Del](2 x^3 - 3 y^2 + 4 z) as output. Thank you. Regards, Rayne URL: ,

 Subject (listing for 'Plotting and defining functions') Author Date Posted Plotting and defining functions Rayne 01/27/07 01:18am Re: Plotting and defining functions yehuda ben-s... 01/28/07 01:50am Re: Plotting and defining functions Rayne 01/29/07 11:30am Re: Plotting and defining functions yehuda ben-s... 01/30/07 02:34am Re: Plotting and defining functions Rayne 01/31/07 05:57am Re: Plotting and defining functions yehuda ben-s... 01/31/07 09:37am Re: Plotting and defining functions Rayne 02/02/07 10:40pm
 Next Comment > Help | Reply To Topic