Postprocessing

What this step does

Library. Each dataset is a frozen copy stored with the project, in its _files folder, and carried in a packed project file. Its origin is recorded:

• a result: the run, the result item, the CAD file and the settings that shaped it;
• an import: the file, the columns and the grouping;
• a derived dataset: the recipe that made it.

Datasets are curves (each series with its own $x$ values), tables or value lists. "Send to Postprocessing" on any Results chart, table or value list adds one.

Import. Text files (.txt, .csv, .tsv, .dat; comment lines are skipped, and a decimal comma is accepted with ; or tab delimiters), spreadsheets (.xlsx, .xlsm; every sheet is a block) and MATLAB files (.mat v5/v7; a v7.3 file must be re-saved with -v7). A long-format table, with many curves in one sheet, can be split by one or more text columns and filtered.

Operations (each makes a new curve):

• difference, sum, ratio and level ratio $10\log_{10}(y_A/y_B)$ of two curves, on A's, B's or both sets of points inside the overlap, interpolated linearly in $x$ or in $\log_{10} x$, never extrapolated;
• octave or third-octave band average: the curve is interpolated on 33 points uniform in $\log f$ across each band and averaged as an energy mean $10\log_{10}\overline{10^{L/10}}$ for levels in dB, or arithmetically otherwise; only bands entirely inside the curve are given;
• centred moving-average smoothing; scale, offset and $x$-scale.

Error metrics. For curve A against reference B on their common points in a chosen $x$ range, with $e = y_A - y_B$: the rms $\sqrt{\overline{e^2}}$, the mean $\bar e$, the median of $|e|$, and the largest $|e|$ with the $x$ at which it occurs. The metrics can be saved as a value list. Value lists can be compared side by side, with differences and percentage differences relative to the first set.

Comparisons. The ticked curves are drawn in one chart with the full chart tools; a chart (its series and view) can be saved by name and reopened.

Source

The band edges follow ISO 266 nominal centres with base-2 edges, as in the program's frequency sweep. The step was validated on a run of the two-baffle test muffler, with a reference transmission loss imported through the import window.

Valid range

Related 1

• Resultsstep.results