Dr. David Harrington

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18 years, 277 days
University of Victoria
Professor or university staff
Victoria, British Columbia, Canada

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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.

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These are replies submitted by dharr

@mehdibgh Perhaps as a way to get initial guesses for fsolve, if the nonlinear problem is close to this...

@Christian Wolinski kk := Matrix(1, 8, {(1, 1) = .500000000000000+0.*I, (1, 2) = 0.1825477032e-15-.5879378012*I, (1, 3) = -.500000000000000+.555570233019603*I, (1, 4) = -0.2691433088e-15-.5879378012*I, (1, 5) = .500000000000000+0.*I, (1, 6) = -0.2691433088e-15+.587937801209679*I, (1, 7) = -.500000000000000-.5555702330*I, (1, 8) = 0.1825477032e-15+.587937801209679*I})

PDEtools:-casesplit seems to be for this purpose, but I've not used it.

@zenterix I was surprised to see the symbols in the plot of floor(x) - they seem to be an "added extra" just for floor(x). They can be enhanced by symbolsize = 20, symbol = solidcircle, but Maple doesn't seem to have them for more complicated functions. You could add symbols yourself by combining the line plot you have with plots with style=point, symbol=solidcircle and style=point, symbol=circle. The three plots could be combined using plots:-display. However, you would have to calculate the endpoints separately, and not using the floor function.

Edit: See plot,discont for more info on getting better discont detection and other options.

@vs140580 See ?ExcelTools,Export. Just write a row of the matrix (or a row vector), specifying the start cell for it.

@vs140580 Your matrix says it has dimensions 83,16, but when I copy it into Maple, I get an error saying it is actually 83x256. So I remove the "83,16" and then try to export the 83x256 Matrix to Excel. Now I get an error message saying the number of columns has to be 255 or less. I'm not sure if this is an Excel limitation, or limitation of my version of Maple (2015). Perhaps this will run for you. You could export the transposed Matrix, or export to another format, e.g., csv.


@vs140580 So for methanol you want to convert "CO" to a graph with two vertices and an edge between them?

pysmiles does this in python, though output is in networkx format. But I assume that the code could be fairly easily converted to Maple. 

IUPAC to SMILES (Simplified molecular-input line-entry system) is going to be difficult. For simple molecules, just search Wikipedia for the molecule (try methanol) and it likely has the SMILES string there on the right side of the page. SMILES is based on spanning trees with information on where the cycles are broken, so generating a graph from it should be straightforward. Likewise generating the missing hydrogens is straightforward. There is specialized software for this (the Wikipedia page may be a starting place for that; I don't have any experience with this). If you just want to draw the molecule, ChemDraw can take a SMILES string as input.

If you want a Maple Graph from SMILES, you will need to think more about it - how do you want to distinguish the vertices for different atoms, or is the bare connectivity all you want? What exactly do you mean by chemical graph?

@tomleslie My assumption is that there is a track along the curve. The ball is dropped (or more accurately thrown down, since initial velocity is non-zero) and rolls down the track; as the track curves it forces the x-direction to change. 

@JAMET Well, it's difficult to be sure because you didn't upload your worksheet, but the * after plots:-pointplot suggests you are using 2D input and have a space there that should not be there.

@Joe Riel Thanks; I'd never noticed that. I see now the help page has comptype with the key option more prominently explained than in my version.

@zenterix As I pointed out the problem is with the range. The function goes to r=infinity, so if you do not specify a plot range, Maple tries to choose one, thinking you will want to see all those really big numbers. If you right-click on your original plot (cmd-click on Mac), choose probe info and then cursor position, and run your cursor over the plot, you will see that the x axis runs in a very narrow range around 2, and the y axis runs from about -60000 to 8000. Your polarplot was also a vertical line at 2, it is just that the range was very large, so it looked like at vertical line at zero. In general, if you see a weird plot, you should modify the range to be where you think the most information is.

@Hullzie16 Although these have "I" in they are actually real, as you have seen. You can remove the I with evalc and then simplify - but now you have trig functions

[-10/3-(10/3)*3^(1/2)*sin(-(1/3)*arctan((3/173)*3^(1/2)*373^(1/2))+(1/3)*Pi)-(10/3)*sin((1/3)*arctan((3/173)*3^(1/2)*373^(1/2))+(1/6)*Pi), -10/3+(10/3)*3^(1/2)*sin(-(1/3)*arctan((3/173)*3^(1/2)*373^(1/2))+(1/3)*Pi)-(10/3)*sin((1/3)*arctan((3/173)*3^(1/2)*373^(1/2))+(1/6)*Pi), -10/3+(20/3)*sin((1/3)*arctan((3/173)*1119^(1/2))+(1/6)*Pi)]


Download CubicSolve.mw

@jud In general it's poor etiquette to delete a post after it has been answered. Perhaps it will be useful for someone else (the indexing ds[2] is not obvious for example but you had figured that out.) Happy to help in your transition to Maple.

@salauayobami Click the green up-arrow, then Choose the file. Then click "upload". Then perhaps after a delay depending on how complicated your worksheet is you should see the two options "Insert link" and "insert contents". Sometimes "Insert contents" does not work well, so just do "insert link". If that doesn't work, suggest you remove the output from the worksheet by Edit->Remove Output -> From worksheet, and try again.

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