Plotting a python dict in order of key values
PythonMatplotlibPython Problem Overview
I have a python dictionary that looks like this:
In[1]: dict_concentration
Out[2] : {0: 0.19849878712984576,
5000: 0.093917341754771386,
10000: 0.075060643507712022,
20000: 0.06673074282575861,
30000: 0.057119318961966224,
50000: 0.046134834546203485,
100000: 0.032495766396631424,
200000: 0.018536317451599615,
500000: 0.0059499290585381479}
They keys are type int, the values are type float64. Unfortunately, when I try to plot this with lines, matplotlib connects the wrong points (plot attached). How can I make it connect lines in order of the key values?
Python Solutions
Solution 1 - Python
Python dictionaries are unordered. If you want an ordered dictionary, use collections.OrderedDict
In your case, sort the dict by key before plotting,
import matplotlib.pylab as plt
lists = sorted(d.items()) # sorted by key, return a list of tuples
x, y = zip(*lists) # unpack a list of pairs into two tuples
plt.plot(x, y)
plt.show()
Solution 2 - Python
Simply pass the sorted items from the dictionary to the plot()
function. concentration.items()
returns a list of tuples where each tuple contains a key from the dictionary and its corresponding value.
You can take advantage of list unpacking (with *
) to pass the sorted data directly to zip, and then again to pass it into plot()
:
import matplotlib.pyplot as plt
concentration = {
0: 0.19849878712984576,
5000: 0.093917341754771386,
10000: 0.075060643507712022,
20000: 0.06673074282575861,
30000: 0.057119318961966224,
50000: 0.046134834546203485,
100000: 0.032495766396631424,
200000: 0.018536317451599615,
500000: 0.0059499290585381479}
plt.plot(*zip(*sorted(concentration.items())))
plt.show()
sorted()
sorts tuples in the order of the tuple's items so you don't need to specify a key
function because the tuples returned by dict.item()
already begin with the key value.