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  #1  
Old 07-15-2015
qin tian qin tian is offline
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Default determine warm-up time

heresays: "While several methods have been presented for determining warm-up time (Law and Kelton, 1991), the easiest and most straightforward approach, although not necessarily the most reliable, is to run a preliminary simulation of the system, preferably with several (3 to 5) replications, and observe at what time the system reaches statistical stability. The length of each replication should be relatively long and allow even rarely occurring events, such as infrequent downtimes, to occur at least two or three times. To determine a satisfactory warm-up period using this method, one or more key response variables should be monitored by period over time, like the average number of entities in a queue or the average utilization of a resource. This approach assumes that the mean value of the monitored response variable is the primary indicator of convergence rather than the variance, which often appears to be the case. If possible, it is preferable to reset the response variable after each period rather than track the cumulative value of the variable, since cumulative plots tend to average out instability in data. Once these variables begin to exhibit steady-state, we can add a 20% to 30% safety factor and be reasonably safe in using that period as the warm-up period. This approach is simple, conservative and usually satisfactory. "

It is easy to track the cumulative value of a variable (eg average queue length vs time) using dashboard in flexsim. I wonder if there is an easy way to plot non-cumulative average queue length (eg every one hour's queue length vs time) using dashboard?
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Old 07-15-2015
qin tian qin tian is offline
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Default

Another question, if it's more conservative to determine warm-up time using cumulative plot instead of non-cumulative plot?
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Old 07-16-2015
Jing Chen
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Wink Customize a dashboard chart

HI! qin
As far as I know the Dashboard is very flexible.
You can calculate “queue length” or any data when running the model and assign it to a node(ex: a lable or a new node under variable) every hour.
And then use "Content vs Time"-Statistics-Custom in dashboard to exhibit a line chart.
If you can read Chinese, you can look this thread (http://www.flexsim.asia/viewthread.p...extra=page%3D1) about how to customize a dashboard chart.
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