Linear regression by least squares method

[mechairoi]

Added leastSquaresForecast linearRegression function for graphs the liner regression by least squares method.

[yuuki]

👍

[shoichimasuhara1982]

👍

[JeanFred]

Would you be able to provide a test for that new method?

[mechairoi]

@JeanFred Thank you for the advice. I have written a test.

[Songmu]

@JeanFred Thank you for the review.

We heavily use graphite in our monitoring SaaS Mackerel for two years. @mechairoi he is in our team.

This feature is very useful for us (and all users, of cource).

We hope this pull request to be accepted.

[JeanFred]

Thanks for writing this test @mechairoi!
This looks fine to me, but as a recent maintainer I would much prefer someone else has a look to it (poke @obfuscurity ?)

[obfuscurity]

This is probably a dumb question, but does it make sense to default startSourceAt to the from parameter?

[mechairoi]

These arguments are copied from the timeSlice function, but it sounds great.

Does it also make sense to default endSourceAt to the until as follows?

--- a/webapp/graphite/render/functions.py
+++ b/webapp/graphite/render/functions.py
@@ -2389,7 +2389,7 @@ def linearRegressionAnalysis(series):
     offset = (sumII * sumV - sumIV * sumI) /denominator - factor * series.start
     return factor, offset

-def linearRegression(requestContext, seriesList, startSourceAt, endSourceAt="now"):
+def linearRegression(requestContext, seriesList, startSourceAt=None, endSourceAt=None):
   """
   Graphs the liner regression function by least squares method.

@@ -2407,8 +2407,8 @@ def linearRegression(requestContext, seriesList, startSourceAt, endSourceAt="now
   """
   results = []
   sourceContext = requestContext.copy()
-  sourceContext['startTime'] = parseATTime(startSourceAt)
-  sourceContext['endTime'] = parseATTime(endSourceAt)
+  if startSourceAt is not None: sourceContext['startTime'] = parseATTime(startSourceAt)
+  if endSourceAt is not None: sourceContext['endTime'] = parseATTime(endSourceAt)

[mechairoi]

@obfuscurity Thank you for the review. I fixed default startSourceAt and endSourceAt. Please let me know if you have any concerns.

[Songmu]

@obfuscurity @JeanFred
How about it?

[JeanFred]

@Songmu Looks good to me ; but still too junior to press the merge button :)

[brutasse]

@JeanFred do it :)

[JeanFred]

All right, let’s do this then :) @mechairoi, would you be able to squash this?

[mechairoi]

@JeanFred squashed :)

[JeanFred]

Aaaaaaand done!

[Songmu]

😄