I am running an SVR prediction on some time series data, and I am receiving this weird offset between my actual and predicted values.

I found this SVM Regression lag post, that mentions adding a lag of 2 data points behind, instead of one. However, I am not sure how to incorporate that into my code (which I've included below).

Does anyone have any ideas on why my predicted vs. actual is offset in this manner?

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My code is as follows:

#! /usr/bin/python

import math
import statistics
import visualizer
import numpy as np
from datagen import constructData
from sklearn import svm

# Applies Support Vector Regression to the electricity dataset,
# prints out the accuracy rate to the terminal and plots
# predictions against actual values
def suppVectorRegress():

    kernelList = ["linear","rbf",polyKernel]
    names = ["linear","radial basis","poly"]
    preds = []

    # Retrieve time series data & apply preprocessing
    data = constructData()

    cutoff = len(data)-30
    xTrain = data[0][0:cutoff]
    yTrain = data[1][0:cutoff]
    xTest = data[0][cutoff:]
    yTest = data[1][cutoff:]

    # Fill in missing values denoted by zeroes as an average of
    # both neighbors

    # Logarithmically scale the data
    xTrain = [[math.log(y) for y in x] for x in xTrain]
    xTest = [[math.log(y) for y in x] for x in xTest]
    yTrain = [math.log(x) for x in yTrain]

    # Detrend the time series
    indices = np.arange(len(data[1]))
    trainIndices = indices[0:cutoff]
    testIndices = indices[cutoff:]
    detrended,slope,intercept = statistics.detrend(trainIndices,yTrain)
    yTrain = detrended

    for gen in range(len(kernelList)):

        # Use SVR to predict test observations based upon training observations
        pred = svrPredictions(xTrain,yTrain,xTest,kernelList[gen])
        # Add the trend back into the predictions
        trendedPred = statistics.reapplyTrend(testIndices,pred,slope,intercept)
        # Reverse the normalization
        trendedPred = [np.exp(x) for x in trendedPred]
        # Compute the NRMSE
        err = statistics.normRmse(yTest,trendedPred)

        print ("The Normalized Root-Mean Square Error is " + str(err) + " using kernel " + names[gen] + "...")



    # Change the parameters 2017,2,1 based on the month you want to predict.
    visualizer.comparisonPlot(2017,2,1,preds,names,plotName="Support Vector Regression Load Predictions vs. Actual", 
        yAxisName="Predicted Kilowatts")

# Construct a support vector machine and get predictions
# for the test set
# Returns a 1-d vector of predictions
def svrPredictions(xTrain,yTrain,xTest,k):
    clf = svm.SVR(C=2.0,kernel=k)
    return clf.predict(xTest)

# A scale invariant kernel (note only conditionally semi-definite)
def polyKernel(x,y):
    return (np.dot(x,y.T)+1.0)**0.95

if __name__=="__main__":

1 Answer 1


Two things that come to my mind:

A) - have you compared the distributions with a Kolgomorov Smirnov Test or similar - (aka: are they really the same. Sure there is the big spike but besides its not that similar (by eye))

B) - Are training and test in the same magnitudes for the input data? If they are not this might confuse your SVR.


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