MaplePrimes - answers and comments on Question, PLOTTING HUGE ARRAYS

more details please

Doug Meade — Wed, 22 Aug 2007 16:52:12 Z

Maple has no trouble reading large amounts of data from a file. Converting data to the format needed for pointplot should not be that difficult. For a large collection of data, it would probably be even better to directly create the appropriate PLOT3D data structure (see ?plot3d,structure). If you can provide a sample of your data, or other details, someone on this list will almost certainly be able to provide more explicit details for how you can create the plot you seek. Looking forward to learning more about your problem, Doug

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Douglas B. Meade
Math, USC, Columbia, SC 29208  E-mail: mailto:meade@math.sc.edu       
Phone:  (803) 777-6183         URL:    http://www.math.sc.edu/~meade/

Pointplot

Mariner — Wed, 22 Aug 2007 16:55:17 Z

What is the format of your input file? Is it possible to manipulate your data with, say Excel, into rows of corresponding X and Y data arranged in columns? If, so Maple can import such data and a command or two can transform it into the format needed by plots,pointplot. However, the plot produced by 5000 points will look a bit crowded, so it may be necessary to plot every, say, 100th point. Again, Maple can do this easily. J. Tarr

Statistics:-PointPlot

DJKeenan — Wed, 22 Aug 2007 19:06:36 Z

Have you looked at Statistics:-PointPlot? If x and y are lists, then Statistics:-PointPlot(y,xcoords=x) should work well. I just tried it with 5000 points (in Maple 11), and it worked fine; response time was <2 seconds.

Sorry, wrong question

ndattani — Thu, 23 Aug 2007 02:41:19 Z

WOW..you guys are GREAT...i'm impressed with the speed and helpfulness of your responses. I actually realized that I asked the wrong question though.. What I have is a text file in VI, with two columns full of numbers, like: R1 R2 1..2.4 2..2.5 3..9.6 I want to create a 3rd and 4th column (R3 and R4), where R3=1/R1^2 and R4 = some complicated function of R2 and R1. Then I want to plot R4 vs R3! I am used to using Tecplot for Unix, and it reads my datafile perfectly and the 3rd and 4th columns are computed and plotted..but tecplot only keeps a certain number of digits when doing its computations, so my 4th column is not as accurate as I need. So I was wondering if Maple could read my datafile in the format that it's in and recognize the fact that there's two columns worth of information, and if I could do calculations on those columns. I tried writing a program in FORTRAN 77 to do these calculations, but although I'm fully familiar with the logic, I am having trouble with the programming language. I am aware of the fact that Excel can EASILY make the 3rd and 4th columns using the formula function, but I was wondering if Maple could do it as well. Thanks a lot guys!

Reading Data Files

gkokovidis — Thu, 23 Aug 2007 03:31:08 Z

On my PC, in the temp directory, I created a test filed called testdata2.dat. The file looks like this if you open it.

R1        R2
0.4059    61.155616
0.406     67.890816
0.4061    71.123712
0.4062    71.39312
0.4063    69.911376
0.4064    67.082592
0.4065    64.119104
0.4066    61.425024
0.4067    59.404464
0.4068    58.326832
0.4069    58.326832
0.4070    59.000352

In Maple, I read it in like this: >restart: >RD:=readdata(`c:/temp/testdata2.dat`,2); >RD; >nops(RD); >X:=[seq(RD[i,1],i=1..nops(RD))]; >Y:=[seq(RD[i,2],i=1..nops(RD))]; Now you can process the X and Y data to create new variables as you see fit. Regards, Georgios Kokovidis Dräger Medical

zip and map

Doug Meade — Thu, 23 Aug 2007 04:10:21 Z

Continuing Georgios' comments, here is how I would suggest combining the lists X and Y to create new columns.

R3 := map( x->1/x^2, X );
R4 := zip( (x,y)->F(x,y), X, Y );

where F(x,y) is the appropriate "complicated function of R2 and R1". There are other ways to do this, but using map and zip is much more efficient than an explicit loop. You can now plot the appropriate lists using the previously suggested methods. Doug

---------------------------------------------------------------------
Douglas B. Meade
Math, USC, Columbia, SC 29208  E-mail: mailto:meade@math.sc.edu       
Phone:  (803) 777-6183         URL:    http://www.math.sc.edu/~meade/