Appropriate formula

[mdsdoha]

Dear Experts!

I am little confused about the issue of using real data to drive model and model behaviour drives the model. I have discussed few experts. Some of them told me that I can use real data to drive the model but others denied to agree on it. They preferred to generate model behaviour from model components. I do not have any problem with replication of both. But, in some cases, reality behaves crazy and completely beyond expectation. Such as production 1000 units sudden drops to 0 or near Zero due to different calamities like natural disaster, finance and so on. Even it is beven be possible to predict such disaster.
Is there any suggestion on it? I need to clear about it.

My second question is, I need such a formula or function where I can enter certain amount of input for certain time then will take out the input and then again will enter more input and the same way I will takes out after certain period. I can use step function but it gives me consistent addition. I want something like which will stop adding input after certain time and will back to the normal and then again will add some and back to normal again. waiting for some valuable and effective sugegstions. Thanks.

MDSDOHA

[tomfid]

There are some drawbacks to using real data - it can be a lot of work, and it can add features to your model that distract from a simple understanding of its behavior.

However, the benefits often outweigh the drawbacks. Using real data may help you to discover problems in the model or the data, and is essential if you want to use the model+data to measure parameters.

If you want to construct arbitrary test inputs, more complicated than STEP, PULSE, RAMP etc. permit, a lookup table may be convenient.