# Spline
# Usage
This function is used to calculate cubic spline interpolation of input series.
Name: SPLINE
Input Series: Only support a single input series. The type is INT32 / INT64 / FLOAT / DOUBLE.
points: Number of resampling points.
Output Series: Output a single series. The type is DOUBLE.
Note: Output series retains the first and last timestamps of input series. Interpolation points are selected at equal intervals. The function tries to calculate only when there are no less than 4 points in input series.
# Examples
# Assigning number of interpolation points
Input series:
+-----------------------------+------------+
| Time|root.test.s1|
+-----------------------------+------------+
|1970-01-01T08:00:00.000+08:00| 0.0|
|1970-01-01T08:00:00.300+08:00| 1.2|
|1970-01-01T08:00:00.500+08:00| 1.7|
|1970-01-01T08:00:00.700+08:00| 2.0|
|1970-01-01T08:00:00.900+08:00| 2.1|
|1970-01-01T08:00:01.100+08:00| 2.0|
|1970-01-01T08:00:01.200+08:00| 1.8|
|1970-01-01T08:00:01.300+08:00| 1.2|
|1970-01-01T08:00:01.400+08:00| 1.0|
|1970-01-01T08:00:01.500+08:00| 1.6|
+-----------------------------+------------+
SQL for query:
select spline(s1, "points"="151") from root.test
Output series:
+-----------------------------+------------------------------------+
| Time|spline(root.test.s1, "points"="151")|
+-----------------------------+------------------------------------+
|1970-01-01T08:00:00.000+08:00| 0.0|
|1970-01-01T08:00:00.010+08:00| 0.04870000251134237|
|1970-01-01T08:00:00.020+08:00| 0.09680000495910646|
|1970-01-01T08:00:00.030+08:00| 0.14430000734329226|
|1970-01-01T08:00:00.040+08:00| 0.19120000966389972|
|1970-01-01T08:00:00.050+08:00| 0.23750001192092896|
|1970-01-01T08:00:00.060+08:00| 0.2832000141143799|
|1970-01-01T08:00:00.070+08:00| 0.32830001624425253|
|1970-01-01T08:00:00.080+08:00| 0.3728000183105469|
|1970-01-01T08:00:00.090+08:00| 0.416700020313263|
|1970-01-01T08:00:00.100+08:00| 0.4600000222524008|
|1970-01-01T08:00:00.110+08:00| 0.5027000241279602|
|1970-01-01T08:00:00.120+08:00| 0.5448000259399414|
|1970-01-01T08:00:00.130+08:00| 0.5863000276883443|
|1970-01-01T08:00:00.140+08:00| 0.627200029373169|
|1970-01-01T08:00:00.150+08:00| 0.6675000309944153|
|1970-01-01T08:00:00.160+08:00| 0.7072000325520833|
|1970-01-01T08:00:00.170+08:00| 0.7463000340461731|
|1970-01-01T08:00:00.180+08:00| 0.7848000354766846|
|1970-01-01T08:00:00.190+08:00| 0.8227000368436178|
|1970-01-01T08:00:00.200+08:00| 0.8600000381469728|
|1970-01-01T08:00:00.210+08:00| 0.8967000393867494|
|1970-01-01T08:00:00.220+08:00| 0.9328000405629477|
|1970-01-01T08:00:00.230+08:00| 0.9683000416755676|
|1970-01-01T08:00:00.240+08:00| 1.0032000427246095|
|1970-01-01T08:00:00.250+08:00| 1.037500043710073|
|1970-01-01T08:00:00.260+08:00| 1.071200044631958|
|1970-01-01T08:00:00.270+08:00| 1.1043000454902647|
|1970-01-01T08:00:00.280+08:00| 1.1368000462849934|
|1970-01-01T08:00:00.290+08:00| 1.1687000470161437|
|1970-01-01T08:00:00.300+08:00| 1.2000000476837158|
|1970-01-01T08:00:00.310+08:00| 1.2307000483103594|
|1970-01-01T08:00:00.320+08:00| 1.2608000489139557|
|1970-01-01T08:00:00.330+08:00| 1.2903000494873524|
|1970-01-01T08:00:00.340+08:00| 1.3192000500233967|
|1970-01-01T08:00:00.350+08:00| 1.3475000505149364|
|1970-01-01T08:00:00.360+08:00| 1.3752000509548186|
|1970-01-01T08:00:00.370+08:00| 1.402300051335891|
|1970-01-01T08:00:00.380+08:00| 1.4288000516510009|
|1970-01-01T08:00:00.390+08:00| 1.4547000518929958|
|1970-01-01T08:00:00.400+08:00| 1.480000052054723|
|1970-01-01T08:00:00.410+08:00| 1.5047000521290301|
|1970-01-01T08:00:00.420+08:00| 1.5288000521087646|
|1970-01-01T08:00:00.430+08:00| 1.5523000519867738|
|1970-01-01T08:00:00.440+08:00| 1.575200051755905|
|1970-01-01T08:00:00.450+08:00| 1.597500051409006|
|1970-01-01T08:00:00.460+08:00| 1.619200050938924|
|1970-01-01T08:00:00.470+08:00| 1.6403000503385066|
|1970-01-01T08:00:00.480+08:00| 1.660800049600601|
|1970-01-01T08:00:00.490+08:00| 1.680700048718055|
|1970-01-01T08:00:00.500+08:00| 1.7000000476837158|
|1970-01-01T08:00:00.510+08:00| 1.7188475466453037|
|1970-01-01T08:00:00.520+08:00| 1.7373800457262996|
|1970-01-01T08:00:00.530+08:00| 1.7555825448831923|
|1970-01-01T08:00:00.540+08:00| 1.7734400440724702|
|1970-01-01T08:00:00.550+08:00| 1.790937543250622|
|1970-01-01T08:00:00.560+08:00| 1.8080600423741364|
|1970-01-01T08:00:00.570+08:00| 1.8247925413995016|
|1970-01-01T08:00:00.580+08:00| 1.8411200402832066|
|1970-01-01T08:00:00.590+08:00| 1.8570275389817397|
|1970-01-01T08:00:00.600+08:00| 1.8725000374515897|
|1970-01-01T08:00:00.610+08:00| 1.8875225356492449|
|1970-01-01T08:00:00.620+08:00| 1.902080033531194|
|1970-01-01T08:00:00.630+08:00| 1.9161575310539258|
|1970-01-01T08:00:00.640+08:00| 1.9297400281739288|
|1970-01-01T08:00:00.650+08:00| 1.9428125248476913|
|1970-01-01T08:00:00.660+08:00| 1.9553600210317021|
|1970-01-01T08:00:00.670+08:00| 1.96736751668245|
|1970-01-01T08:00:00.680+08:00| 1.9788200117564232|
|1970-01-01T08:00:00.690+08:00| 1.9897025062101101|
|1970-01-01T08:00:00.700+08:00| 2.0|
|1970-01-01T08:00:00.710+08:00| 2.0097024933913334|
|1970-01-01T08:00:00.720+08:00| 2.0188199867081615|
|1970-01-01T08:00:00.730+08:00| 2.027367479995188|
|1970-01-01T08:00:00.740+08:00| 2.0353599732971155|
|1970-01-01T08:00:00.750+08:00| 2.0428124666586482|
|1970-01-01T08:00:00.760+08:00| 2.049739960124489|
|1970-01-01T08:00:00.770+08:00| 2.056157453739342|
|1970-01-01T08:00:00.780+08:00| 2.06207994754791|
|1970-01-01T08:00:00.790+08:00| 2.067522441594897|
|1970-01-01T08:00:00.800+08:00| 2.072499935925006|
|1970-01-01T08:00:00.810+08:00| 2.07702743058294|
|1970-01-01T08:00:00.820+08:00| 2.081119925613404|
|1970-01-01T08:00:00.830+08:00| 2.0847924210611|
|1970-01-01T08:00:00.840+08:00| 2.0880599169707317|
|1970-01-01T08:00:00.850+08:00| 2.0909374133870027|
|1970-01-01T08:00:00.860+08:00| 2.0934399103546166|
|1970-01-01T08:00:00.870+08:00| 2.0955824079182768|
|1970-01-01T08:00:00.880+08:00| 2.0973799061226863|
|1970-01-01T08:00:00.890+08:00| 2.098847405012549|
|1970-01-01T08:00:00.900+08:00| 2.0999999046325684|
|1970-01-01T08:00:00.910+08:00| 2.1005574051201332|
|1970-01-01T08:00:00.920+08:00| 2.1002599065303778|
|1970-01-01T08:00:00.930+08:00| 2.0991524087846245|
|1970-01-01T08:00:00.940+08:00| 2.0972799118041947|
|1970-01-01T08:00:00.950+08:00| 2.0946874155104105|
|1970-01-01T08:00:00.960+08:00| 2.0914199198245944|
|1970-01-01T08:00:00.970+08:00| 2.0875224246680673|
|1970-01-01T08:00:00.980+08:00| 2.083039929962151|
|1970-01-01T08:00:00.990+08:00| 2.0780174356281687|
|1970-01-01T08:00:01.000+08:00| 2.0724999415874406|
|1970-01-01T08:00:01.010+08:00| 2.06653244776129|
|1970-01-01T08:00:01.020+08:00| 2.060159954071038|
|1970-01-01T08:00:01.030+08:00| 2.053427460438006|
|1970-01-01T08:00:01.040+08:00| 2.046379966783517|
|1970-01-01T08:00:01.050+08:00| 2.0390624730288924|
|1970-01-01T08:00:01.060+08:00| 2.031519979095454|
|1970-01-01T08:00:01.070+08:00| 2.0237974849045237|
|1970-01-01T08:00:01.080+08:00| 2.015939990377423|
|1970-01-01T08:00:01.090+08:00| 2.0079924954354746|
|1970-01-01T08:00:01.100+08:00| 2.0|
|1970-01-01T08:00:01.110+08:00| 1.9907018211101906|
|1970-01-01T08:00:01.120+08:00| 1.9788509124245144|
|1970-01-01T08:00:01.130+08:00| 1.9645127287932083|
|1970-01-01T08:00:01.140+08:00| 1.9477527250665083|
|1970-01-01T08:00:01.150+08:00| 1.9286363560946513|
|1970-01-01T08:00:01.160+08:00| 1.9072290767278735|
|1970-01-01T08:00:01.170+08:00| 1.8835963418164114|
|1970-01-01T08:00:01.180+08:00| 1.8578036062105014|
|1970-01-01T08:00:01.190+08:00| 1.8299163247603802|
|1970-01-01T08:00:01.200+08:00| 1.7999999523162842|
|1970-01-01T08:00:01.210+08:00| 1.7623635841923329|
|1970-01-01T08:00:01.220+08:00| 1.7129696477516976|
|1970-01-01T08:00:01.230+08:00| 1.6543635959181928|
|1970-01-01T08:00:01.240+08:00| 1.5890908816156328|
|1970-01-01T08:00:01.250+08:00| 1.5196969577678319|
|1970-01-01T08:00:01.260+08:00| 1.4487272772986044|
|1970-01-01T08:00:01.270+08:00| 1.3787272931317647|
|1970-01-01T08:00:01.280+08:00| 1.3122424581911272|
|1970-01-01T08:00:01.290+08:00| 1.251818225400506|
|1970-01-01T08:00:01.300+08:00| 1.2000000476837158|
|1970-01-01T08:00:01.310+08:00| 1.1548000470995912|
|1970-01-01T08:00:01.320+08:00| 1.1130667107899999|
|1970-01-01T08:00:01.330+08:00| 1.0756000393033045|
|1970-01-01T08:00:01.340+08:00| 1.043200033187868|
|1970-01-01T08:00:01.350+08:00| 1.016666692992053|
|1970-01-01T08:00:01.360+08:00| 0.9968000192642223|
|1970-01-01T08:00:01.370+08:00| 0.9844000125527389|
|1970-01-01T08:00:01.380+08:00| 0.9802666734059655|
|1970-01-01T08:00:01.390+08:00| 0.9852000023722649|
|1970-01-01T08:00:01.400+08:00| 1.0|
|1970-01-01T08:00:01.410+08:00| 1.023999999165535|
|1970-01-01T08:00:01.420+08:00| 1.0559999990463256|
|1970-01-01T08:00:01.430+08:00| 1.0959999996423722|
|1970-01-01T08:00:01.440+08:00| 1.1440000009536744|
|1970-01-01T08:00:01.450+08:00| 1.2000000029802322|
|1970-01-01T08:00:01.460+08:00| 1.264000005722046|
|1970-01-01T08:00:01.470+08:00| 1.3360000091791153|
|1970-01-01T08:00:01.480+08:00| 1.4160000133514405|
|1970-01-01T08:00:01.490+08:00| 1.5040000182390214|
|1970-01-01T08:00:01.500+08:00| 1.600000023841858|
+-----------------------------+------------------------------------+