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sakamali
Turkey
33 Posts |
 Posted - 25 Jul 2012 : 07:48:44
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Hi,
I have purchased your product in order to use SPC components.I have a problem in EWMA chart. In this type of chart there exists some values to set up initially. like :
spcChart.ChartData.EWMA_StartingValue = 10; // Set to estimate of mean of process variable.
spcChart.ChartData.EWMA_Lambda = 0.1;
spcChart.DefaultControlLimitSigma = 2.7; // Specifies L value
spcChart.ChartData.EWMA_UseSSLimits = false;
My aim is set the spcChart.ChartData.EWMA_StartingValue to process mean , that is calculated according to input data . Initally this value is 1.0 . How can I set this value to calculated process mean.
Thank you in advance
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quinncurtis
1586 Posts |
Posted - 25 Jul 2012 : 09:41:50
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I am not sure exactly what you want to do. Normally, a process engineer would have a very good idea as to estimate of the mean of a process, before you start to apply EWMA control rules to it. You set that using the EWMA_StartingValue parameter. If the mean of the process is completely unknown, you could just pick any starting, EWMA_StartingValue, run the EWMA chart, then write down the resulting target (center line) value, which will be the mean. Then, in all future runs of the EWMA chart for the given process, use that as the EWMA_StartingValue.
If you absolutely must have everything automatically calculated, you will need to run the same data through twice. The first time using any value for the EWMA_StartingValue. You can then obtain the mean using GetControlLimitData. Reset the data of the chart back to empty using ResetSPCChartData. Then, use that mean as the starting value, and run the data again.
// Run your data through once using any value for EWMA_StartingValue.
this.ChartData.EWMA_StartingValue = 1; // Set to estimate of mean of process variable.
SimulateData(20,10);
// Calculate the SPC control limits for both graphs of the current SPC chart
this.AutoCalculateControlLimits();
// NO need to display the chart, since for initial run
// this.RebuildChartUsingCurrentData();
// Get calculated mean of process
double meanValue = PrimaryChart.GetControlLimitData(SPCChartObjects.SPC_CONTROL_TARGET).LimitValue;
this.ChartData.EWMA_StartingValue = meanValue; // Set to estimate of mean of process variable.
// Reset the chart back to empty
this.ChartData.ResetSPCChartData();
this.ChartData.EWMA_StartingValue = meanValue; // Set to estimate of mean of process variable.
// Simulate some more data
SimulateData(20, 10);
// Calculate the SPC control limits for both graphs of the current SPC chart
this.AutoCalculateControlLimits();
// Scale the y-axis of the chart to display all data and control limits
this.AutoScalePrimaryChartYRange();
// Rebuild the chart using the current data and settings
this.RebuildChartUsingCurrentData(); |
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EWMA Starting Value Problem
