如何在熊猫图中为每条线绘制水平线？

Question

I need to draw a horizontal line from the first point in each line drawn below. The line spans from first xticks to last x-ticks. To use ax.hlines() , I need to know the xmax and and xmin which I do not know if the x-values are categorical. How to draw these horizontal lines (The lines given in dotted pink lines.)?

mydf = DataFrame( [[0.70, 0.79, 0.89, 0.76],
               [0.73, 0.79, 0.80, 0.67],
               [0.74, 0.70, 0.79, 0.87],
               [0.74, 0.60, 0.79, 0.7],
               [0.74, 0.79, 0.79, 0.7]])
mydf.columns = ['f1', 'f2','f3','f4']
mydf.index = ['a','b','c','d','e']
ax = mydf.plot()
ax.set_xticks(range(len(mydf.index)))
ax.set_xticklabels([item for item in mydf.index.tolist()])

Answer 1

You do not need to loop over the columns. You can simply add the below line to plot the lines.

All the y parameters for the lines would be the starting points. mydf.iloc[0] , xmin would always be ax.get_lim()[0] and xmax would be ax.get_lim()[1] .

See docs for more information.

ax.hlines(mydf.iloc[0], ax.get_xticks().min(), ax.get_xticks().max(), linestyle='--', color='pink')

Output:

Answer 2

Use:

mydf = pd.DataFrame( [[0.70, 0.79, 0.89, 0.76],
               [0.73, 0.79, 0.80, 0.67],
               [0.74, 0.70, 0.79, 0.87],
               [0.74, 0.60, 0.79, 0.7],
               [0.74, 0.79, 0.79, 0.7]])

mydf.columns = ['f1', 'f2','f3','f4']
mydf.index = ['a','b','c','d','e']

ax = mydf.plot()
ax.set_xticks(range(len(mydf.index)))
ax.set_xticklabels([item for item in mydf.index.tolist()])

for i in range(len(mydf.columns)):
    ax.axhline(y=mydf.iloc[0,i], xmin=.05, xmax=.95, ls='--', color='pink')

where

xmin : scalar, optional, default: 0 Should be between 0 and 1, 0 being the far left of the plot, 1 the far right of the plot.

xmax : scalar, optional, default: 1 Should be between 0 and 1, 0 being the far left of the plot, 1 the far right of the plot.