mqr.spc.rules.

n_trending#

mqr.spc.rules.n_trending(n)#

Rule monitoring the count of trending points.

This function returns an alarm rule that alarms when n statistics in a row trend (up or down).

This function generates a rule. The result of this function is another function that can be passed to mqr.plot.spc.alarms or combine.

Parameters:

nint: Number of sample in a trend required to cause an alarm.

Returns:

Callable[(ControlStatistic, ControlParams), pandas.Series[bool]]: A function taking a control statistic and the params used to create them, and returning a series with True marking alarms.

Examples

data = pd.DataFrame({
    'Xbar': np.array([11, 9, 12, 10, 9, 8, 12])
#                            ^^^^^^^^^^^^ (4 trending)
})

params = mqr.spc.XBarParams(centre=10, sigma=1)
stat = params.statistic(data)
rule = mqr.spc.rules.n_trending(4)

fig, ax = plt.subplots(figsize=(7, 3))
mqr.plot.spc.chart(stat, params, ax=ax)
mqr.plot.spc.alarms(stat, params, rule, ax=ax)

(Source code, png, pdf)

../../_images/mqr-spc-rules-n_trending-1.png