+- HP Forums (https://www.hpmuseum.org/forum)
+-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html)
+--- Forum: HP Prime (/forum-5.html)
+--- Thread: define a formula (/thread-874.html)
define a formula - fefer92 - 03-09-2014 10:44 PM
Hi,
I have hp prime and I would like to define a formula to make my calculus easy and faster,the formula is annexed here,anybody can help me please?
Thanks
RE: define a formula - Stefan - 03-09-2014 11:40 PM
Unless you absolutely want to write a function for that (for learning purposes maybe) you don't have to:
1. You could use the mean(L,p) function where L is the list of values and p the list of probabilities.
2. Or if you write L and p as vectors you could just calculate the dot product of the vectors L and p: [L1, L2, L3,...]*[p1, p2, p3...]
If p1, p2, etc are not probabilities in range 0 to 1, but frequencies instead (e.g. 3 times, 7 times etc) for method 2 you should also divide by sum(p): E(X)=L*p/sum(p)
RE: define a formula - fefer92 - 03-09-2014 11:56 PM
(03-09-2014 11:40 PM)Stefan Wrote: Unless you absolutely want to write a function for that (for learning purposes maybe) you don't have to:
1. You could use the mean(L,p) function where L is the list of values and p the list of probabilities.
2. Or if you write L and p as vectors you could just calculate the dot product of the vectors L and p: [L1, L2, L3,...]*[p1, p2, p3...]
If p1, p2, etc are not probabilities in range 0 to 1, but frequencies instead (e.g. 3 times, 7 times etc) for method 2 you should also divide by sum(p): E(X)=L*p/sum(p)
Thank you,that really help a little,but I have many formulas similar to this one,like this formula annexed below and I would like to know how to make this one to ...
RE: define a formula - Stefan - 03-10-2014 12:10 AM
lol, expectancy, entropy... looks like your studying for the same exam than I do :-D
Here you can again use the dotproduct and make use of the fact that you can apply most of the functions to lists and vectors.
log_2(p) applies log_2 to the vector p (the log_n(x) template is in the math templates).
And then just multiply p and log_2(p), just as before: H(x)=p*log_2(p)
P.S: You can type equations in this forum in Latex syntax if you surround them with two $ in the front and back:
$$\frac{1}{x}$$
RE: define a formula - fefer92 - 03-10-2014 01:05 AM
(03-10-2014 12:10 AM)Stefan Wrote: lol, expectancy, entropy... looks like your studying for the same exam than I do :-D
Here you can again use the dotproduct and make use of the fact that you can apply most of the functions to lists and vectors.
log_2(p) applies log_2 to the vector p (the log_n(x) template is in the math templates).
And then just multiply p and log_2(p), just as before: H(x)=p*log_2(p)
P.S: You can type equations in this forum in Latex syntax if you surround them with two $ in the front and back:
$$\frac{1}{x}$$
I'm learning in a subject that is called principle of communication II (Hehehe).The dot tip is a good idea,I didn't understood the H(x),you have to make a sum and the PS too,can you try to explain in another way?
Thanks
RE: define a formula - Stefan - 03-10-2014 01:38 AM
(03-10-2014 01:05 AM)fefer92 Wrote: I didn't understood the H(x)I just wrote the H(x) to indicate that this is the complete formula for the entropy. There is no need to enter the H(x) into the calc.
The P.S: instead of including an image for the equations you can write them right away in the text in LaTeX and make two $ around the equation. So e.g. writing
Code:
$$\frac{1}{x}$$