Using matplotlib to plot text

Question

I'm trying to put text in a graph, but for some reason I can't do it using plt.text. I get the

TypeError: can only concatenate list ("not float") to list

I don't really know what to change to get this working.

x = [3, 1, 4, 5, 1]
y = [5, 4, 4, 3, 7]

fig=plt.figure(1)
ax = fig.add_subplot(1, 1, 1)
plt.xlim(0.5, 7)
plt.ylim(0, 7.5)

ax.spines['left'].set_position('center')
ax.spines['bottom'].set_position('center')

ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')

ax.xaxis.set_ticks_position('bottom')
ax.yaxis.set_ticks_position('left')

plt.scatter(x, y, marker="x", color="red")

Names=['name1', 'name2', 'name3', 'name4', 'name4']

plt.text(x + 0.1, y + 0.1, Names, fontsize=9)

The error is not with text, it's with x+0.1 and y+0.1, which you would be more aware of if you processed and posted the whole error — Mad Physicist
– Mad Physicist, Commented Sep 25, 2018 at 11:34
The error was with trying to use all Names at once in plt.text and adding 0.1 to x and y which are of type list — Sheldore
– Sheldore, Commented Sep 25, 2018 at 11:41

Sheldore · Accepted Answer · 2018-09-25 11:44:28Z

2

You are trying to use plt.text in a vectorised manner. It won't work that way. You were also adding 0.1 (a float) to x (a list) and hence the self-explanatory error. You have to loop over your Names and use the corresponding x and y value and put the text one name at a time. You can do it using enumerate as follows

Names=['name1', 'name2','name3','name4','name4']
for i, name in enumerate(Names):
    plt.text(x[i]+0.1, y[i]+0.1, name, fontsize=9)

edited Sep 25, 2018 at 11:44

answered Sep 25, 2018 at 11:37

Sheldore

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Comments

Mad Physicist · Accepted Answer · 2018-09-25 12:15:06Z

There are two errors in your code.

The one that is raising is that you attempt to add a scalar to a Python list: x + 0.1 and y + 0.1. + is defined as concatenation, which is what the error is telling you. You can potentially fix this by converting x and y to numpy arrays ahead of time. For arrays, + is defined as element-wise addition, as you were expecting. However, this won't solve your second problem.

The documentation for pyplot.text explicitly states that the x and y inputs are scalars: you can only plot one string per call. That means you need a loop:

for x_, y_, name in zip(x, y, Names):
    plt.text(x_ + 0.1, y_ + 0.1, name, fontsize=9)

Please read your errors carefully and post the whole thing next time.

Perhaps you should add +0.1 to x_ and y_ to avoid the text overlapping the markers

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