Struggling to plot multiple columns against x using Pandas dataframe from .txt file

Question

I am trying to plot several graphs on the same plot using a pandas dataframe, but I'm getting an error probably because I'm not doing it properly and I can't figure it out. Below is a screenshot of my code (sorry the code formatter tool isn't working): Code

And I keep getting ''ValueError: x and y must be the same size''. Just for reference here is the data I am trying to plot, with the R column on the x axis and the specified columns on the x axis: Dataframe

IHMO, scatter only accept one x and one y at a time. Also, you don't need to do SAPT_data=pd.DataFrame(SAPT_data): pd.read_csv returns a DataFrame already. — Quang Hoang
– Quang Hoang, Commented Nov 18, 2020 at 18:45

Guillaume Vergnolle · Accepted Answer · 2021-10-15 19:00:04Z

1

Have you tried :

for column in ['exch', 'IND2', 'elst', 'dHf', 'DISP2'] :
    SAPT_DATA.plot(x="R", y=column, kind="scatter")

It should solve your problem since scatter only takes one column for the 'y' argument

EDIT :

If you want to have everything in one plot, with lines between points and special markers, you can use the following arguments for the plot function :

fig, ax = plt.subplots()
for column in ['exch', 'IND2', 'elst', 'dHf', 'DISP2'] :
    SAPT_DATA.plot(x="R", y=column, style='o-', ax=ax)
plt.show()

edited Oct 15, 2021 at 19:00

answered Nov 18, 2020 at 18:50

Guillaume Vergnolle

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2 Comments

avidominusnox Over a year ago

Thank you, I tried this out and it gave me the plots but it gave me them separately whereas I want them all on the same graph. Also, do you know how I can make all the points in the scatter joined up with a line like how it's done in matplotlib?

Guillaume Vergnolle Over a year ago

If you want a line between them you shouldn't use the scatter argument. Instead, draw a regular plot and add markers on each points by using the following code : fig, ax = plt.subplots() then SAPT_DATA.plot(x='R', y=column, style='o-', ax=ax)

avidominusnox · Accepted Answer · 2020-11-18 19:18:54Z

0

Update: Graph using teepee's method

answered Nov 18, 2020 at 19:18

avidominusnox

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Comments

teepee · Accepted Answer · 2020-11-18 22:05:17Z

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You can only do one value in the y because it's a scatter plot. Intead, you should melt your data frame (df.melt(...)) using "R" as the id_var and the other 5 columns as your value_vars and then use seaborn or altair to plot these:

import seaborn as sns
df = df.melt(id_var='R',
             value_vars=['exch', 'IND2', 'elst', 'dHF', 'DISP2'],
             var_name='energy_type',
             value_name='energy')
sns.relplot(data=df, x='R', y='energy', hue='energy_type')

Side note: you are making a dataframe out of a dataframe in your code, but that doesn't cause an error; just something redundant to eliminate.

edited Nov 18, 2020 at 22:05

answered Nov 18, 2020 at 18:51

teepee

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2 Comments

avidominusnox Over a year ago

Amazing, thanks! I tried this out and it gave me it all on one graph which is what I wanted however I have a few issues (I have posted my graph below as an answer since I can't include images in comments): 1) I assumed 'variable' was free to edit to make whatever variable it is that these points represent, in my case it's energies, but when I changed it to 'energies' it didn't let me. 2) Is there any way I can join the points up with curves going through each of them like in matplotlib line plots?

teepee Over a year ago

Yes that can be done using the var_name and value_name arguments in the melt method (I have edited it to reflect that now).

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