Difference between revisions of "Modeling"

From wiki
Jump to navigation Jump to search
Line 1: Line 1:
 
Mostly based on [http://greenteapress.com/ModSimPy/ModSimPy.pdf this paper] that comes with its own modsim library.
 
Mostly based on [http://greenteapress.com/ModSimPy/ModSimPy.pdf this paper] that comes with its own modsim library.
  
=Eyeopeners=
+
* A model depicts a system.
* Store results in a [[Python:DataTypes#List|list]]
+
* The state of the system attributes is stored in a [[Pandas#Series]]
<syntaxhighlight lang=python>
+
* Results of how the system attributes change over time are stored in Pandas Series too (1 Series per attribute).
for a in range(100):
+
* Parameters that determine how the system attributes change are stored in a [[Python:DataTypes#Dictionary_or_dict|dictionary]] or also in a pandas series.
    funcAresults[a] = functionAcall(bla,bla)
+
* The functions that change the system attributes take the system parameters as parameter. This way you can play with the parameter values to get the best result.
    funcBresults[a] = functionBcall(bla,bla)
+
* [[Numpy#linspace]] provides an equally distributed range of values so you can play easily between the limits you set.  
</syntaxhighlight>
+
* The quality of the model can be judged by calculating the relative error of the [[Approximation]] 
: ModSimPy is using Series from [[Pandas]] to store results. This adds handy functions like.
+
 
* The state of the model is stored in a Pandas Series too.
+
=Other remarks=
* Put other interesting metrics in the state object too.
 
 
* If you use randomness in a function, get the mean values of several runs.
 
* If you use randomness in a function, get the mean values of several runs.
* Check the effect of different parameter values using [[Numpy]] [[Numpy#linspace | linspace]].
+
 
 +
=Example code=
 +
[[Numpy]] [[Numpy#linspace | linspace]]
 
<syntaxhighlight lang=python>
 
<syntaxhighlight lang=python>
 
funcAresults = pd.Series([])
 
funcAresults = pd.Series([])
Line 21: Line 22:
 
     print(funcAresults)
 
     print(funcAresults)
 
</syntaxhighlight>
 
</syntaxhighlight>
* The [https://en.wikipedia.org/wiki/Approximation_error Approximation error] ([https://nl.wikipedia.org/wiki/Benaderingsfout benaderingsfout]) is the difference between a calculated value and the real value. By dividing it by the real value you get the relative error. A bit relative error indicates bad calculation.
+
 
The largest relative error between two arrays as percentage:
+
Store results in a [[Pandas]] [[Pandas#Series|Series]]
 
<syntaxhighlight lang=python>
 
<syntaxhighlight lang=python>
max(abs(calculated - real) / real ) * 100
+
for a in range(100):
 +
    funcAresults[a] = functionAcall(bla,bla)
 +
    funcBresults[a] = functionBcall(bla,bla)
 
</syntaxhighlight>
 
</syntaxhighlight>

Revision as of 15:36, 25 December 2018

Mostly based on this paper that comes with its own modsim library.

  • A model depicts a system.
  • The state of the system attributes is stored in a Pandas#Series
  • Results of how the system attributes change over time are stored in Pandas Series too (1 Series per attribute).
  • Parameters that determine how the system attributes change are stored in a dictionary or also in a pandas series.
  • The functions that change the system attributes take the system parameters as parameter. This way you can play with the parameter values to get the best result.
  • Numpy#linspace provides an equally distributed range of values so you can play easily between the limits you set.
  • The quality of the model can be judged by calculating the relative error of the Approximation

Other remarks

  • If you use randomness in a function, get the mean values of several runs.

Example code

Numpy linspace

funcAresults = pd.Series([])
p1_array = np.linspace(0,1,12)
for p1 in p1_array:
    for a in range(50):
        funcAresults[a] = functionAcall(p1,p2)
    print(funcAresults)

Store results in a Pandas Series

for a in range(100):
    funcAresults[a] = functionAcall(bla,bla)
    funcBresults[a] = functionBcall(bla,bla)