Python code with for loop that did not work

Question

I have run the following code but it showed an empty plot with nothing plotted and I am not able to know the reason Please help

import matplotlib.pyplot as plt
import math
for xx in range(10,100000,1000):
    plt.plot(xx,math.sqrt((.30*(1-.3))/(xx-1)))

See pyplot.plot(...). plot takes list of values to be plotted. you provide a single integer. kindly peruse matplotlib.org/tutorials/introductory/sample_plots.html and the API of stuff you want to use before asking here. Thanks. — Patrick Artner
– Patrick Artner, Commented Apr 19, 2019 at 15:16
Questions that ask "please help me" tend to be looking for highly localized guidance, or in some cases, ongoing or private assistance, which is not suited to our Q&A format. It is also rather vague, and is better replaced with a more specific question. Please read Why is “Can someone help me?” not an actual question?. — Patrick Artner
– Patrick Artner, Commented Apr 19, 2019 at 15:19

Michael Silverstein · Accepted Answer · 2019-04-19 15:18:19Z

4

If you are trying to plot each point individually, try using plt.scatter() like this:

for xx in range(10,100000,1000):
    plt.scatter(xx, math.sqrt((.30*(1-.3))/(xx-1)))

If you're looking to plot a continuous line, you'll want to make your vectors beforehand and then pass them to plt.plot(). I suggest using numpy since np.arrays can handle vectorized data

import numpy as np
# Make x vector
xx = np.arange(10,100000,1000)
# Make y
y = np.sqrt((.30*(1-.3))/(xx-1))
# Plot
plt.plot(xx, y)

answered Apr 19, 2019 at 15:18

Michael Silverstein

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Comments

Sheldore · Accepted Answer · 2019-04-19 16:42:23Z

While the other answer solves the issue, you should know that your attempt was not completely wrong. You can use plt.plot to plot individual points in a for loop. However, you will have to specify the marker in that case. This can be done using, let's say, a blue dot using bo as

for xx in range(10,100000,1000):
    plt.plot(xx,math.sqrt((.30*(1-.3))/(xx-1)), 'bo')

Alternatively, in addition to the other answer, you can simply use plt.scatter even for a whole array as following. Note, in this case you will have to use the sqrt module from NumPy as you are performing vectorized operation here which is not possible with math.sqrt

xx = np.arange(10,100000,1000)
plt.scatter(xx,np.sqrt((.30*(1-.3))/(xx-1)), c='green', edgecolor='k')

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