Variables evaluation

Variables evaluation - Symbolic to numerical substitution and evaluation - Messages

#1 Posted: 4/12/2022 4:14:10 PM
Mario Acevedo

Mario Acevedo

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Dear all:

I am new to Smath Studio, great software!

Even I am new to its usage, I am trying quite complicated calculations I guess.

I am putting the following lines:

substitution.png

As you can see, I am using Maxima plugin and the Maxima function ev() to substitute values in the symbolic variable. I have some specific questions:
1.) Is there an alternative way to do this kind of calculations without using the Maxima plugin?
2.) v is a system of values, each value is an equality, is there an automatic way to generate a system of values?

Thank to all the people that could help.
#2 Posted: 4/12/2022 5:04:06 PM
Martin Kraska

Martin Kraska

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I can't open your image. From what you describe, you might want to use the substitution function at() from Custom Functions plugin.

at.sm (22 KiB) downloaded 33 time(s).
Martin Kraska Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx
#3 Posted: 4/12/2022 6:16:56 PM
Jean Giraud

Jean Giraud

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Attach your Smath document.
#4 Posted: 4/12/2022 6:51:35 PM
Jean Giraud

Jean Giraud

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at(3) Demo.PNG
#5 Posted: 4/12/2022 7:41:47 PM
Mario Acevedo

Mario Acevedo

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Sorry about the image, now the image is visible.

What I want is to iterate over a set o values to substitute in a variable a store the results in a variable, something like this:

substitution.png

Is there a way to do this substitutions in an iterative way?.
I mean: using a set of programming lines?

In this worksheet I copied and pasted the lines to perform the iterations, but in a general problem solving it is desirable to iterate automatically.
#6 Posted: 4/12/2022 8:20:21 PM
Mario Acevedo

Mario Acevedo

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Here is the Worksheet:

Worksheet1.sm (10 KiB) downloaded 29 time(s).
#7 Posted: 4/12/2022 8:45:20 PM
Mario Acevedo

Mario Acevedo

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Thank you Martin Kraska, at works fine and is what I needed.

It seems that to iterate I have to declare the sys vector by myself, isn't it?

Thanks a lot!
#8 Posted: 4/12/2022 9:29:50 PM
Jean Giraud

Jean Giraud

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Wrote

What I want is to iterate over a set o values to substitute in a variable a store the results in a variable, something like this:


An iterative process is a solving process.
As you say, you just want to plug something from command line.

Command Line UNK.PNG
#9 Posted: 4/12/2022 11:45:16 PM
Mario Acevedo

Mario Acevedo

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wow!, this is what I was looking for!!!, THANK YOU very much Jean Giraud!

#10 Posted: 4/13/2022 7:41:58 AM
sergio

sergio

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I take inspiration from Jean, but I use the Vectorize function and I forget the size of U

Show Spoiler


FunzioniVettori.sm (6 KiB) downloaded 26 time(s).
sergio
#11 Posted: 4/13/2022 8:21:09 AM
Martin_B

Martin_B

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Pay attention! The definition of M(r) doesn't make much sense.

Screenshot 2022-04-13 131758.png
#12 Posted: 4/13/2022 8:41:51 AM
Jean Giraud

Jean Giraud

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Wrote

I take inspiration from Jean, but I use the Vectorize function and I forget the size of U


Superb Sergio ... added in the main document.
#13 Posted: 4/13/2022 9:48:44 AM
overlord

overlord

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An algorithm can also be used.
It may be simpler by this way.

Regards

Worksheet1_algorithm.sm (4 KiB) downloaded 32 time(s).

2022-04-13_15-46.png
#14 Posted: 4/13/2022 2:10:35 PM
Mario Acevedo

Mario Acevedo

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Nice implementation!!

Just a question, does the S variable had to be declared and dimensioned previous to its use?

I will try the code asap!

Thank you !
#15 Posted: 4/13/2022 2:48:08 PM
Martin_B

Martin_B

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You should always define variables used as arrays in function before assigning elements.

Worksheet1_algorithm.sm (8 KiB) downloaded 25 time(s).

Screenshot 2022-04-13 194527.png
1 users liked this post
sergio 4/13/2022 4:00:00 PM
#16 Posted: 4/13/2022 4:04:10 PM
Jean Giraud

Jean Giraud

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Wrote

Just a question, does the S variable had to be declared and dimensioned previous to its use ?


No, it sets by itself within the for loop.
Wise to clear within the algo ... U:=0
That will avoid interaction with else U above document.
Algo style is an immense companion in Smath.
Personally, I use it as much as possible,
it enables the local command line.
Cheers ... Jean.

Maths algo style MATRIX in_extenso.sm (5 KiB) downloaded 26 time(s).


#17 Posted: 4/13/2022 4:47:50 PM
overlord

overlord

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Wrote

You should always define variables used as arrays in function before assigning elements.


MarB is dead right.
Array variables should be considered carefully if they will be redefined multiple times.
Or they can be undefined and named uniquely. I tend to name variables in functions this way.
You can find below how I would name your functions variables.
Pretends mess of misusage.

Regards

worksheet1.png
#18 Posted: 4/13/2022 5:55:24 PM
Davide Carpi

Davide Carpi

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Wrote

Just a question, does the S variable had to be declared and dimensioned previous to its use?



It isn't required but it is good practice. If the variable name already exists you might fall in some unexpected cases when the dimensions are different. In addition to the above suggestions, you can use also a Clear(S) as initializer.
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