Set order of y axis in python with Matplotlib

Question

I am trying to plot simple arrays with values a,b,c and d. I want to plot these arrays in alphabetical order. For example I added a plot of the fifth row in the dataframe given below, the y-value starts at 'a' (good) and then the next y-value is 'c' (wrong), I want to have 'b' at that place. In short; the y values should be in alphabetical order without losing the x value order.

The head of the dataset is given. It is very basic.

And the (very basic) code bins = ['a', 'b', 'c', 'd']; plt.plot((X_sax.iloc[4,:])); plt.yticks(bins);

Can Someone help me?

Thanks!

Probably you can just enclose your y axis list in sorted(), but if you post your code we can know for sure. — B. Bogart
– B. Bogart, Commented Nov 2, 2020 at 14:18
Welcome to Stack Overflow! Please take a moment to read How do I ask a good question?. You need to provide a Minimal, Complete, and Verifiable example that includes a toy dataset (refer to How to make good reproducible pandas examples) — Diziet Asahi
– Diziet Asahi, Commented Nov 2, 2020 at 14:20

B. Bogart · Accepted Answer · 2020-11-02 14:55:31Z

1

I would map the y axis to values and then name the axis as @Yogesh suggested.

from matplotlib import pyplot as plt  
X_sax = list('accbcbbbbcb')

datamap = {'a':1,'b':2,'c':3, 'd':4}
X_sax = list(map(lambda x: datamap[x], X_sax))
           
plt.plot((X_sax))
plt.yticks([1,3,2,4], bins)

gives:

answered Nov 2, 2020 at 14:55

B. Bogart

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Comments

Arty · Accepted Answer · 2020-11-02 16:53:34Z

1

Next code uses NumPy-only functions for very fast processing of data:

import matplotlib.pyplot as plt, pandas as pd, numpy as np
# ----- Input -----
bins = ['a', 'b', 'c', 'd']
X_sax = pd.DataFrame(data = np.array([list('accbcbbbbcb')]))
print(X_sax)
# ----- Show ------
v = X_sax.values[0, :] # Choose which row to show
b = np.sort(bins)
v = np.searchsorted(b, v)
plt.plot(v)
plt.yticks(np.arange(b.size), b)
plt.show()

You may also try code above online!

Output:

   0  1  2  3  4  5  6  7  8  9 10
0  a  c  c  b  c  b  b  b  b  c  b

and

edited Nov 2, 2020 at 16:53

answered Nov 2, 2020 at 15:57

Arty

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Comments

Yogesh · Accepted Answer · 2020-11-02 14:51:13Z

0

Use this:

plt.yticks(np.arange(len_of_y_ticks), y_order)

Eg:

x = np.arange(0, 11)
y = 'a c c b c b b b b c b'.split()
y_order = sorted(set(y))
len_of_y_ticks = len(set(y))
y = list(map(lambda x: ord(x)-97, y))
plt.plot(x, y)
plt.yticks(np.arange(4), y_order)
plt.show()

edited Nov 2, 2020 at 14:51

answered Nov 2, 2020 at 14:29

Yogesh

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2 Comments

BramAdafruit Over a year ago

Thanks for you response. Now i get the same output as graph above, only b and c are swapped. But i want that the graph handles the data also in alphabetical order. Not only changing the ticks. The value 'c' should be considered higher than 'a' and 'b'.

Yogesh Over a year ago

Oh I see, in that case add y = list(map(lambda x: ord(x)-97, y)) before plt.plot(x, y). I have edited the main code, now hopefully it satisfies you.

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