absay - 6 months ago 27

Python Question

I'm working on time series with Dynamic Time Warping. I need to plot the alignment between the datapoints of two sequences:

`t=[t1,t2,t3,...,tx]`

s=[s1,s2,s3,...,sy]

The length of both sequences may vary. I also have which points match, say:

`[(1,1),(1,2), (2,2), (3,3), (4,3), (4,4)]`

This is read as:

`t[1] matches s[1]`

t[1] matches s[2]

t[2] matches s[2]

...

t[4] matches s[4]

What I want to achieve is something like this:

Or even better, like this (i.e. nothing but the two sequences and their alignment):

I'm aware of the existence of the

`dtw`

Summarizing, I just need to know how to plot both sequences, one on top of the other (subplots might help, I believe?) and draw a line between each datapoint using Python.

Answer

You should be able to plot s and t with plt.plot. Doing the lines between them is a little trickier. I'm assuming that the x-axis corresponds to the xth element of both s and t. In that case, if the ith element of s and the jth element of t are paired, you could plot the line between them with `plt.plot((i, j), (s[i], t[j]), color = 'black')`

```
import matplotlib.pyplot as plt
#plot signals
plt.plot(y1, label = 'Signal 1')
plt.plot(y2, label = 'Signal 2')
#plot alignment
for i, j in matches:
plt.plot((i, j), (y1[i], y2[j]), color = 'black')
plt.show()
```