# Normalization vs Standardization for multivariate time-series

I'm using DTW as a distance measure for comparing two multivariate time-series. I want to be able to cluster data using DTW as distance measure, since time-series may be shifted, skewed.

Since there are a couple of parameters I should normalize the series so that all the parameters have the same influence when trying to determine whether time-series are similar. I'm using Euclidean distance as local distance for DTW.

My question is - how to determine whether I should use normalization (subtract min and divide by max) or standardization (subtract mean and divide by standard deviation)?

Moreover, can anyone explain to me what is the point with standardization? I understand that it can help me determine how many standard deviations are values far from their mean, but why would that improve my similarity measure when comparing two time-series?

I'm not a statistician, so any explanation would be great. I understand that normalization would give me values in range [0,1] so that all parameters have values in same range, but what will I get by standardization?

Finally, should I divide each time-series by the standard deviation of the whole dataset, or only by standard deviation of the time-series I'm standardizing?

I must also emphasize that my data does not belong to a normal distribution.

• Normalization in your sense would appear to be (value $-$ min) / (max $-$ min), not as described. – Nick Cox Apr 22 '19 at 9:13

I recommend reading http://www.dataminingblog.com/standardization-vs-normalization/

A couple of points, I usually prefer standardization over normalization since normalization suffers even more from outliers. However since you stated that your data is not normal, I would recommend trying (X-median)/IQR or winsoring (clipping the top and bottom 0.1%) before doing standardization.

If you know the distribution of your data, you could use the appropriate functions. For example, geometric mean for log-normal.

As always, it is best to test the methods to see which one performs best.