erik10

I have a degree in Mathematics and Physics from the Danish University Aarhus, comparable to a masters degree with thesis - majoring in Mathematics. In 1991-92 I was a visting scholar at UCLA, Los Angeles, following graduate courses in Applied Mathematics. Since 1992 I have been a teacher in a high school (gymnasium) in Denmark. Special interests: Applied mathematics, graphics and popularizing Mathematics.

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These are questions asked by erik10

Dear Maple users

I just created a sunflower in Maple using the Golden angle. See attached file. I am using a scatterplot with solidcircles as symbols. But what I would like now is to plot integers instead of the solidcircles in order to investigate the order of these different solidcircles. To make it clear: I have 500 solidcircles. They have been plottet using two vectors containing the x and y coordinates of the individual solidcircles. The n'th solidcircle I want to replace with the integer n. How can I create that different plot?

NB! The plot might need to be larger or the integers smaller, but that is fine. 

 

Regards

Erik V

sunflower.mw

Dear Maple users

I have been looking in the Maple help menu for categorical plots or charts, and haven't been able to find an appropriate one. I hope someone can help me. I am looking for something like the following, which I have been drawing:

Regards,

Erik V.

Dear Maple users

I wanted to create a list of random datapoints for the "simple linear regression model". Standard deviation sigma is given, slope a and fixed value b given for the line as well. Before the code below I had some random x-values created for the data points saved in the list X. To calculate the corresponding y-values randomly from a normal distribution with standard deviation sigma and mean equal to a*x+b I wrote the code below:

 

randomize():
for i from 1 by 1 to N do    
    mean:=a*X[i]+b:
    Yvar:=RandomVariable(Normal(mean,sigma));
    S:=Sample(Yvar,1);
    Z[i]:=S[1];
end do:
Y:=convert(Z,list):

....

 

It actually works, but I just found it a bit strange having to repeatedly ask for a random sample with only a single member. Isn't it possible to do it more efficiently? I am aware of the special properties of the normal distribution, which would make it possible to take only one sample and add the mean afterwards, but I am not looking for ad hoc solutions, rather appropriate commands to create simgle random values from a distribution.  

Erik

 

Dear Maple users

I wanted to export two long lists X and Y of data into two columns in Excel by using the Export command from the ExcelTools package. Data was however exported into rows! I converted the lists into vectors and I succeeded in doing it the way I wanted:

with(ExcelTools);
X1 := convert(X, Vector);
Y1 := convert(Y, Vector);
Export(X1, "data1.xlsx", 1, "A1");
Export(Y1, "data1.xlsx", 1, "B1");

But is it really necessary to convert to vectors in order to accomplish this task? 

Regards,

Erik


 

Dear Maple users

Some students have come to us to report, that something doesn't seem to work properly in Maple 2019.1 in Document Mode. And they seem to be right: writing an passive math formula by using Shift+F5 (the formula is gray, not blue), then using F5 to get out of that Math field and back into Text Mode. Using the Enter key to go to the next line: It doesn't work! The cursor stays in the same line. This behavior is new in Maple 2019. It worked properly in Maple 2018 and earlier. I assume it is not the intention? 

I know it can easily be dealt with by making a new Paragraph by using the shortcut Ctrl+Shift+J. I call the assumed bug 'severe' though, because it will severely delay the workflow for many students. They are used to deliver a document mixed with formulas (active or passive) and text. 

NB! I have tested it on several computers (Mac and Windows), and it doesn't work on any of them.

Regards,

Erik V.

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