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Excerpt

This example illustrates you to apply percentile functions.

Functions:

D generate list excerpts
pages MEDIAN Function,PERCENTILE Function,QUARTILE Function,APPROXIMATEMEDIAN Function,APPROXIMATEPERCENTILE Function,APPROXIMATEQUARTILE Function

Source:

The following table lists each student's height in inches:

StudentHeight
164
265
363
464
562
666
766
865
969
1066
1173
1269
1369
1461
1564
1661
1771
1867
1973
2066

Transformation:

Use the following transformations to calculate the median height in inches, a specified percentile and the first quartile.

• The first function uses a precise algorithm which can be slow to execute across large datasets.
• The second function uses an appropriate approximation algorithm, which is much faster to execute across large datasets.
• These approximate functions can use an error boundary parameter, which is set to `0.4` (0.4%) across all functions.

Median: This transformation calculates the median value, which corresponds to the 50th percentile.

D trans
RawWrangle true 'medianIn' step derive type: single value: median(heightIn) as: 'medianIn' Formula type Single row formula Formula median(heightIn) New column name New formula

D trans
RawWrangle true 'approxMedianIn' step derive type: single value: approxmedian(heightIn, 0.4) as: 'approxMedianIn' Formula type Single row formula Formula approximatemedian(heightIn, 0.4) New column name New formula

Percentile: This transformation calculates the 68th percentile.

D trans
RawWrangle true 'percentile68In' step derive type: single value: percentile(heightIn, 68, linear) as: 'percentile68In' Formula type Single row formula Formula percentile(heightIn, 68, linear) New column name New formula

D trans
RawWrangle true 'approxPercentile68In' step derive type: single value: approximatepercentile(heightIn, 68, 0.4) as: 'approxpercentile68In' Formula type Single row formula Formula approximatepercentile(heightIn, 68, 0.4) New column name New formula

Quartile: This transformation calculates the first quartile, which corresponds to the 25th percentile.

D trans
RawWrangle true 'percentile25In' step derive type: single value: quartile(heightIn, 1, linear) as: 'percentile25In' Formula type Single row formula Formula quartile(heightIn, 1, linear) New column name New formula

D trans
RawWrangle true 'approxPercentile25In' step derive type: single value: approximatequartile(heightIn, 1, 0.4) as: 'approxPercentile25In' Formula type Single row formula Formula approximatequartile(heightIn, 1, 0.4) New column name New formula

Results:

studentIdheightInapproxPercentile25Inpercentile25InapproxPercentile68Inpercentile68InapproxMedianInmedianIn
164646467.166.926666
265646467.166.926666
363646467.166.926666
464646467.166.926666
562646467.166.926666
666646467.166.926666
766646467.166.926666
865646467.166.926666
969646467.166.926666
1066646467.166.926666
1173646467.166.926666
1269646467.166.926666
1369646467.166.926666
1461646467.166.926666
1564646467.166.926666
1661646467.166.926666
1771646467.166.926666
1867646467.166.926666
1973646467.166.926666
2066646467.166.926666

D s also
label example_percentile_functions