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To check the instantaneous value of a variable

#3294  Permalink Top

To check the instantaneous value of a variable

Mar-20-13 14:49:29

Hello
I wish to check the instantaneous value of a variable at a particular time instant. I am currently unable to do so. I am new to the modeling environment, so please excuse me if the question seems rather silly.
I am attaching a sample code below. Its a function x which varies as the square of time. I wish to find the value of x (at say time = 0.4 sec) and store it in another variable (say y) which would be constant. I would like to know the procedure and the syntax to obtain the desired value of y. For example in the following case the value of y should be 0.08.

Code:


model test

Real x;

equation

der(x) = time;

end test;

Thank You for your assistance.

#3296  Permalink Top

Re: To check the instantaneous value of a variable

Mar-20-13 15:05:45

Code:

loadString("model test 

Real x; 

equation 

der(x) = time; 

end test; ");getErrorString();

simulate(test);getErrorString();

y:=val(x, 0.4);getErrorString();

// Create new model with y

loadString("model M

  constant Real y = " + String(y) + "

end M;");getErrorString();

list(M);getErrorString();

Code:

$ omc a.mos

true

""

record SimulationResult

    resultFile = "/home/martin/tmp/test_res.mat",

    simulationOptions = "startTime = 0.0, stopTime = 1.0, numberOfIntervals = 500, tolerance = 0.000001, method = 'dassl', fileNamePrefix = 'test', storeInTemp = false, noClean = false, options = '', outputFormat = 'mat', variableFilter = '.*', measureTime = false, cflags = '', simflags = ''",

    messages = "",

    timeFrontend = 0.009196981,

    timeBackend = 0.004855915000000001,

    timeSimCode = 0.001735353,

    timeTemplates = 0.001114121,

    timeCompile = 0.15997102200000002,

    timeSimulation = 0.008438043000000001,

    timeTotal = 0.185361157

end SimulationResult;

""

0.08000000008381952

""

true

""

"model M

  constant Real y = 0.08;

end M;



"

""

#3300  Permalink Top

Re: To check the instantaneous value of a variable

Mar-21-13 08:12:52

That worked out pretty well. I entered your code in OMShell and it worked just as you had said. Thanks!

I tried to introduce the code into OMedit as the value which I need is to be used further but to no avail. I am getting confused as I don't know where to enter the code. Is there a way of doing so ?

Thanks a lot !
Pratyush

#3301  Permalink Top

Re: To check the instantaneous value of a variable

Mar-21-13 08:59:01

OMEdit has no way of doing this. Sorry.

#3302  Permalink Top

Re: To check the instantaneous value of a variable

Mar-21-13 11:24:59

Oh I see. Anyways are you aware of any other method in which we can store the value of a variable in the middle of a simulation ?
I am actually making a library in OMEdit and one the components needs to have the intermediate values of a variable for further use.

Thanks Again!

#3303  Permalink Top

Re: To check the instantaneous value of a variable

Mar-21-13 11:31:11

Write it to a text-file during simulation or read the result-file after OMEdit simulates a model. You could even write your own external C code to read the result-file during initialization.

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