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468Hello all ... FYI, we will be creating new forums specifically for Q&A geared towards undergraduate students. Our goal is to have a section of the forums that are more suited to the kinds of issues that younger users who have neither the computing or math experience, may have. We'll be uploading the test groups this week and the forums should be live by the end of the week. We'll also do subsequent refinements in the autumn once Will gets back. Tom 4.
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Substitution
Hi
What command do I use to plug a value for x
into an expression and get an answer. I am
thinking here of a biggish expression with just
one variable x in it.
Curious
two-argument eval()
To evaluate an expression at an instance of a variable, use the eval() command in its two-argument form.
For example,
E := sin(x)+x;
eval(E,x=4.0);
That will evaluate E with 4.0 as the value for x.
acer
re: Substitution
FTR.
If you have Maple 11 just right click at the end of your biggish expression , get a long drop down menu, choose <Evaluate at a point>, plug in your point and get an exact answer. If the answer is not a single real number, right click again and choose <Approximate>, <5 digits>.
The Maple output is elegant and informative.
Here is an example that is not elegant nor informative,FWIW.
E := sin(x)+x; @ x=4, = sin(4) + 4 = 3.2423, all done with right clicks but without the long arrows and informative superscripts.
List of points
BYC *
I am having trouble finding help in Help for making a list of points such as
[[a1, sin(a1)], [a2, sin(a2)], .. [an, sin(an)]],
where a1=0 and an=a10=Pi. That's a 20 degree interval.
I can get a column of points but not a row list of points.
asa
* Begging Your Compassion
seq command
You can use the seq command like the following:
[seq([an, sin(an)], an = 0 .. evalf(Pi), evalf((1/10)*Pi))];
this tells maple to loop through values of 0 to Pi at a step of Pi/10. The seq command needs to have numeric values for the range and step and that is why I have an evalf command where Pi is being used.
To get more information on the seq command, check the help page at
?seq
Scott
floats as loop index
I'm never wild about using a float as the index of a loop. If nothing else, the final value will be off slightly from what you want. Better, I feel, to do
Or use an integer index and divide in the list.
hELP w/o Help
Thanks, your point about float well taken.
Although your answer didn't help me on "Help" it
did give me the answer I was looking for.
I didn't know that you could put [ ] outside the command.
This could be a useful example in "Help" somewhere, don't
you think (rhetorically that is)?
help is helpful
I don't understand your request.
The help for seq (?seq) does include examples with both {} and [].
Moreover, both ?[] and ?list give information about forming lists.
You do have to have some idea of what you are trying to do before you would come up with any of these. I don't believe it's unreasonable to expect a user to come up with at least one of these.
You can't expect any system to provide a meaningful response to the question: Tell me what I need to know.
Doug
Help
The help page for seq has a lot of information on it.
You can get to it by executing
?seq
in a Maple worksheet. Alternatively you can open the help system and look for seq.
The 4th and 6th examples at the bottom of the page shows the square brackets outside of the seq() call to make a list. The 7th example shows something like the one that you were asking for (as in a list of points). In the help page there is no example for a floating point as the step value, but the help page does indicate that the step value needs to be a numeric value (in the Parameter section).
If you believe the help page is missing something, could you be a bit more specific what it was that you were looking for, so that someone else reading this will know exactly what you mean?
Scott
Plotting Triangles
How do I plot a triangle with three points A, B, C and then additionally have text inserted at each point corresponding to those points so that they are marked A, B and C? How do I enter text anywhere else?
another way
You can use the geometry package to plot a triangle:
restart; with(geometry):
point(A, 0, 0): point(B, 3, 3): point(C, 0, 2):
triangle(T1, [A, B, C]):
draw(T1, printtext = true, axes = none, color = green, filled = true, title = "My triangle");
Triangle
There are many ways to do this, here is an example.
>restart:
>with(plots):
>triang:=polygonplot([[0,0],[3,3],[0,2]], thickness=2):
>a:=textplot([0,0,"A"],align={ABOVE,RIGHT}):
>b:=textplot([3,3,"B"],align={ABOVE,RIGHT}):
>c:=textplot([0,2,"C"],align={ABOVE,RIGHT}):
>display(triang,a,b,c);
For more help on each of the above commands, look at the help files for polygonplot and for textplot. At the command line, type a question mark followed by the command and hit the enter key:
>?textplot
>?polygonplot
Regards,
Georgios Kokovidis
Dräger Medical
It worked exactly as you
It worked exactly as you stated. Thank-you indeed - and also for the additional help. Now I know exactly where to come with questions re Maple coding. What a terrific thread.
- Olivier
Digits?
What is the Straight Dope on "digits"?
> evalf(Pi); digits := 4; evalf(Pi), "Not 4 digits?"; evalf(Pi, 5); digits, "So why is it still 10 digits?";
3.141592654
4
3.141592654, "Not 4 digits?"
3.1416
4, "So why is it still 10 digits?"
Digits, not digits
Try Digits.
Graphing an Equation in Two Variables; Evaluating Solutions
Thank-you djc for answering my first question here as well. I hope that in time I'll have Maple language down as well as I know so many who have come before me have it.
For now, please forgive these elementary questions. I am new to Maple and a beginning Math major, but I hope as time progresses (and I complete more classes) I will have some more complex questions to pose here, which I hope might be of use to others. Perhaps there are other beginning students who have the same questions I do and, if so, I hope my posing them here will help them. So, here goes:
I'm working on a simple precalculus equation, the graph of the equation y = x^3-2*sqrt(x). I'm plugging in certain coordinates to find if they satisfy the equation and are on the graph. I solved (x,y) for (1,-1) and the equation holds true, but when I use the graphing software to right-click on the equation to get a graph using Plot Builder (2-D Implicit Plot), it shows a curve of points only in quadrant I; however, when I use Evaluate and plug in (1,-1) the equation holds true. Why is (1,-1) not being expressed on the graph, in quadrant IV?
TIA,
Olivier
Please....
Olivier, would you be able to post new questions in a new forum topic in the future?
This way these forum topics don't get too many questions on them and this forum topic shows how diverse the questions can get. This also makes it harder for future beginners to make use of these tips if they are stuck in these long posts on different topics.
Scott