pyplot: Plotting scatter plot with multiple Y values and categorical X values

Question

I'm trying to create a simple scatter plot with metrics data I collect from my experiments. Each day, I test multiple experimental samples and the number of samples varies. I'm trying to create a scatter plot with the days as the x values, and all the experimental values collected on that day as the y values.

I've tried several approaches so far.

I'll spare the full code, but here is an example of what the data looks like:

XVals = ['10-Dec-18', '11-Dec-18']
YVals = [[0.88, 0.78, 0.92, 0.98, 0.91],[0.88, 0.78, 0.92, 0.98]]

Since pyplot wants x and y to be of the same dimension, I tried the following suggestion

for xe, ye in zip(XVals, YVals):
   plt.scatter([xe] * len(ye), ye)

This gives me a value error since my xvals are strings.

ValueError: could not convert string to float: '10-Dec-18'

I have also tried generating the plot in the following fashion, but again I get an error message because x and y are of different dimensions:

fig, ax = plt.subplots()
ax.scatter(XVals, YVals)
plt.show()

This gives me the obvious error:

ValueError: x and y must be the same size

I haven't been able to find any examples of a similar plot (multiple Y values with categorical X values). Any help would be appreciated!

Answer 1

One option is to create flattened lists for the data. The first list, X , will contain the day of each data point. Each day is repeated n times, where n is the number of data points for that day. The second list Y is simply a flattened version of YVals .

import matplotlib.pyplot as plt

XVals = ['10-Dec-18', '11-Dec-18']
YVals = [[0.88, 0.78, 0.92, 0.98, 0.91],[0.88, 0.78, 0.92, 0.98]]

X = [XVals[i] for i, data in enumerate(YVals) for j in range(len(data))]
Y = [val for data in YVals for val in data]

plt.scatter(X, Y)
plt.show()