Home / Statistical Tools / Control Charts / Update Control Charts
Update Control Charts¶
When you add rows to the data a chart was built from, Update rebuilds that chart from the larger range without asking you anything. You do not reopen the dialog and you do not re-enter the settings.
From Excel click...
QXL Stat Tools > Update, with the chart's own worksheet active.
The neighbouring Update Workbook button is not implemented in this version. Pressing it opens a message box saying so and changes nothing, so refresh chart sheets one at a time with Update.
What It Does¶
Quantum XL stores two things when it creates an analysis: the dialog settings, hidden on the output worksheet, and a named range covering the cells the data came from. Update uses both.
- It reads the stored settings off the active worksheet.
- It finds the original data range through that named range, so it does not matter whether you remember where the data was.
- It regrows the range along the axis your data runs in. Column-oriented data grows downward to the last populated cell in each of its columns and keeps the same columns, so a new column beside the block is not picked up. Row-oriented data grows rightward and keeps the same rows. If the source was an Excel Table, it takes the table's current extent instead, which can grow both ways.
- It re-reads the data and re-runs the analysis with the stored settings.
New rows are picked up because of step 3, and the scan for them runs UPWARD from the bottom of the sheet, stopping at the last populated cell in each column. Two consequences are worth knowing:
- A blank row between the old block and the new rows does not stop them being found. The blank rows are pulled into the range as well, and plot as gaps.
- Anything else you have typed lower down the same column is pulled in too. Keep the column below your data clear, or a note parked at the bottom of the sheet becomes a data point.
Data typed into a different column is not part of the range and will not be seen.
What Changes and What Does Not¶
The control limits are recalculated from all the data, including the new rows, when the chart is using its default baseline of every subgroup. That is the usual case.
They are not recalculated if the chart was set to estimate from a fixed baseline. A chart whose Estimate Limits From setting was left on First N keeps the limits it already had, because that setting says which subgroups the estimate comes from, and adding more does not change the first N. New points are plotted against the limits that were already there, and can fall outside them. That is the point of a fixed baseline, and Update respects it rather than quietly widening the band. See Baseline and Limit Estimation.
Every dialog setting survives. The sigma multiplier, the rule set and its thresholds, splits, transformations, capability entries and display choices are all reused exactly. Only the data range, the source worksheet reference and the list of excluded outliers are refreshed.
When the new data no longer fits the column's type¶
Every column carries a data type, and Update re-reads your data against the type the chart was built with. When the new rows no longer fit that type, the chart does not quietly drop them.
The type is widened to fit. A column stored as Count that has since gained a negative number or a fraction is recast as Integer or Continuous, so the value is plotted rather than treated as missing. The change is made in one place before the dialog's lists are built, so the list you see and the chart that is drawn cannot disagree about a column's type.
A type is only ever widened, never narrowed. You chose the type when you built the analysis, and adding data that happens to be all whole numbers is not a reason to take a Continuous column back to Count.
A chart that cannot accept the wider type refuses instead. The P, U and G charts are counted by nature: a negative or fractional count is not a count, so those slots stay at Count and the run stops with a message naming the column, the slot and what the slot will take, in this shape:
The column 'Rejects' is set to Continuous, so it cannot be used for Sample Size, which accepts Count. Change the column's type, or open the analysis and choose a different column for Sample Size.
Modify carries the same answer. The widened type is written back into the dialog's column list, so Modify opens showing the type the chart will actually use rather than the one that was stored.
When Update Is Refused¶
| Situation | What you see |
|---|---|
| The active sheet is not a Quantum XL output sheet | This worksheet does not contain Quantum XL analysis data. followed by Please select a worksheet created by Quantum XL and try again. |
| No analysis of any kind is detected | No Quantum XL analysis was detected on this worksheet. |
| The analysis was built from a single group of data rather than columns or rows | Update is not supported for Single Group Data analyses. followed by Please use Modify instead to change the data range. |
| The original data range can no longer be found, usually because the source sheet was deleted or renamed | The source data for this analysis cannot be found. with the internal reference name |
| The stored settings are unreadable or incomplete | Failed to read analysis settings. or Stored analysis data is incomplete. |
The single-group case is the one worth remembering: use Modify instead, which reopens the dialog with your settings in it and lets you point at a new range.
Charts Made by the Wizard¶
The Control Chart Wizard is not implemented in this build, so no new chart comes from it. A chart built by the wizard in an earlier version is built by the older engine and stores its settings a different way. Update still works on it, but it takes the older code path rather than the one described above.