Anylogic: How to create plot from database table?

Question

In my Anylogic model I succesfully create plots of datasets that count the number of trucks arriving from terminals each hour in my simulation. Now, I want to add the actual/"observed" number of trucks arriving at a terminal, to compare my simulation to these numbers. I added these numbers in a database table (see picture below). Is there a simple way of adding this data to the plot?

I tried it by creating a variable that reads the database table for every hour and adding that to a dataset (like can be seen in the pictures below), but this did not work unfortunately (the plot was empty).

Answer 1

You don't explain why it "didn't work" (what errors/problems did you get?), nor where you defined these elements.

(1) Since you want both observed (empirical) and simulated arrivals per terminal, datasets for each should be in the Terminal agent. And then the replicated plot (in Main) can have two data entries referring to data sets terminals(index).observedArrivals and terminals(index).simulatedArrivals or whatever you name them.

(2) Using getHourOfDay to add to the observed dataset is wrong because that just returns 0-23 (i.e., the hour in the current day for the current model date). Your database table looks like it has hours since model start, so you just want time(HOUR) to get the model time in elapsed hours (irrespective of what the model time unit is). Or possibly time(HOUR) - 1 if you only want to update the empirical arrivals for the hour at the end of that hour (i.e., at the same time that you updated the simulated arrivals).

(3) Using a Variable to get the database value each hour doesn't work because a variable's initial value is only evaluated once at model initialisation. You want an hourly cyclic Event in Terminal instead which adds the relevant row's value. (You need to use the Insert Database Query wizard to generate the relevant Java code for the query you need in the event's action.)

(4) Because you have a database table with specifically-named columns for each terminal (columns terminal_a and presumably terminal_b etc.) that makes it slightly more awkward. (This isn't proper relational table design where, instead of 4 columns for the 4 terminals, you'd instead have two columns for terminal_id and observed_value with a row for each time period and terminal combination.)

So your database query expression (in your Terminal agents) will need to use the SQL format (not the QueryDSL format) so that you can 'stitch in' the correct column name into the SQL.