## dharr

Dr. David Harrington

## 3813 Reputation

18 years, 153 days
University of Victoria
Professor or university staff

## Social Networks and Content at Maplesoft.com

I am a professor of chemistry at the University of Victoria, BC, Canada, where my research areas are electrochemistry and surface science. I have been a user of Maple since about 1990.

## Need an approximate solution...

I have had success in the past with providing an approximate solution. Something like 'approxsoln' = [F(eta) = 1+eta-(1/6)*eta^2, G(eta) = 0, H(eta) = 1-(1/3)*eta]. Presumably you know something about what the solution looks like roughly. Particularly there is not much information about G, only that it is zero at both boundaries.

## Coloured contours...

It's not really an answer, but I do this with a coloured 3-D contour plot where I specify the exact contours I want and then colour the plot according to height using shading =zhue. For example

plot3d(S(X, Y), X = 0 .. X3, Y = 0 .. 1, axes = boxed, orientation = [-90, 0], scaling = constrained, style = surfacecontour, contours = [seq(i/(10.)+0.5e-1, i = 0 .. 9)], shading = zhue, thickness = 3, tickmarks = [6, 4, 3], labels = ["", "", ""], grid = [150, 50]);

You can then have a colour key using

plot3d(X, X = 0 .. 1, Y = 0 .. .2, axes = boxed, orientation = [-90, 0], scaling = constrained, thickness = 2, font = [Times, normal, 20], style = surfacecontour, shading = zhue,thickness=2, tickmarks = [0, 0, 0], labels = [" ", " ", " "],contours=[seq(0.1*i+0.05,i=0..9)]);

## syntax problems...

I can't see the right-hand side of your screen, but two problems come to mind. To define a1 as a function, you need a1:=(r,theta)->sum( etc And for plotting a function you need either plot(a1,0..infinity,0..Pi/2) or plot(a1(r,theta),r=0..infinity,theta=0..Pi/2)

## the worksheet...

I didn't save yesterday, but did it again, with a smaller number of solutions this time (263), though I believe I entered the equations identically. Many of the solutions have many variables zero, so there is a lot of structure here.

## the worksheet...

I didn't save yesterday, but did it again, with a smaller number of solutions this time (263), though I believe I entered the equations identically. Many of the solutions have many variables zero, so there is a lot of structure here.

## changing source...

I found this also. Specifically after entering with the maple button, the code previewed with an image (but not well). When I made the post, the image wasn't there. Looking at the source showed the text had been moved out of the maple tags and put after the closing one. I moved it back in source mode, but it ended up outside again. This behavior was different I think from a few days earlier. Definitely strange.

David

## contourplot...

I see the half plane for x less than 1/2 as red, which is as it should be, since the function is -1 there. For x greater than 1/2 and y negative the function is x*y which is negative and again red. For x greater than 1/2 and y positive, the function is x*y which is now positive and shows yellow. This all seems right to me, and is a little clearer if you try contourplot3d(f(x,y),x=0..1,y=-1..1,contours=[0],filled=true,axes=boxed); and rotate around until you see the 2-D view. As for your first question, I am not so sure... David.

## substituting derivatives...

I did play about with some ways to work with the derivatives (mainly using D) without success; but turning them into derivatives later is a workable solution

## substituting derivatives...

I did play about with some ways to work with the derivatives (mainly using D) without success; but turning them into derivatives later is a workable solution

## LaTeX for Journal submission...

Others have addressed the need Sci. Workplace, especially for LaTeX. Sci Workplace has meant I can produce LaTeX without knowing (much) LaTeX. I could live with some other way of producing nice documents (MathML for example) but the bottom line is I submit papers with math to Journals that can directly typeset from the LaTeX. I use Sci Wrkplace for quickly making notes to myself or for my classes, and use it for simple math to help me make those notes. But for any significant math, I use Maple. Maple is a better math tool, SciWorkplace is a better document production tool.

## LaTeX for Journal submission...

Others have addressed the need Sci. Workplace, especially for LaTeX. Sci Workplace has meant I can produce LaTeX without knowing (much) LaTeX. I could live with some other way of producing nice documents (MathML for example) but the bottom line is I submit papers with math to Journals that can directly typeset from the LaTeX. I use Sci Wrkplace for quickly making notes to myself or for my classes, and use it for simple math to help me make those notes. But for any significant math, I use Maple. Maple is a better math tool, SciWorkplace is a better document production tool.

## simpler?...

A float can be converted to a rational, so the following does something similar (note the decimal point to convert the fraction to a real) convert(77/45.,rational,3); # gives 12/7 convert(77/45.,rational,2); # gives 5/3

## simpler?...

A float can be converted to a rational, so the following does something similar (note the decimal point to convert the fraction to a real) convert(77/45.,rational,3); # gives 12/7 convert(77/45.,rational,2); # gives 5/3

## nops...

try nops (number of operands). I would have expected it to be under ?list, but I see it isn't (in v. 10), which does seems like a serious omission.

## typesetting interpretation of a/bc...

And yet, a/bc is usually interpreted in typeset notation as a/(b*c). In the International Union of Pure and Appled Chemistry rules: "In evaluating combinations of many factors, multiplication takes precedence over division in the sense that a/bc should be interpretaed as a/(bc) rather than (a/b)c; however in complex expressions it is desirable to use brackets to eliminate any ambiguity" Usually the IUPAP (physics) and IUPAC (chemistry) rules are in agreement, and when I write papers with my mathematics colleagure, we also use this convention, so I think it is fairly universal. (I am thinking as it it written on the page, i.e., output, here; I am not suggesting input a/b*c be interpreted this way, since (a/b)*c is the standard programming interpretation of input.)
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