如何 plot 两个系列在 python 中的比例非常不同

Question

I'm a beginner in python. I have to plot two graphs in the same plot. One of my graphs is velocity, which ranges between (-1,1), and the other one is groundwater, which ranges between (10,12). When I use the following code, the graphs become very small.

ax1 = plt.subplot(111)
ax2 = ax1.twinx()
df=pd.read_excel ('final-all-filters-0.6.xlsx')
df['Date']=pd.to_datetime(df['Date'])
date = df['Date']
gwl = df['gwl']
v =df['v']
plt.plot(date,gwl, color='deepskyblue',linewidth=2)
plt.plot(date,v, color='black',linewidth=2)
ax1.grid(axis='y')
ax1.xaxis.set_major_locator(matplotlib.dates.YearLocator())
ax1.xaxis.set_minor_locator(matplotlib.dates.MonthLocator((1,3,5,7,9,11)))
ax1.xaxis.set_major_formatter(matplotlib.dates.DateFormatter("\n%Y"))
ax1.xaxis.set_minor_formatter(matplotlib.dates.DateFormatter("%b"))
ax1.grid(which='minor', alpha=0.3, linestyle='--')
ax1.grid(which='major', alpha=2)
for spine in ax1.spines.values():
        spine.set_edgecolor('gray')
ax1.tick_params(axis='x',  which='both', colors='gray')
ax1.tick_params(axis='y', colors='gray')
ax1.set_ylabel('v', color='g')
ax2.set_ylabel('GWL', color='b')
plt.show()

But when I add the ax1.set_ylim(-1, 1) and ax2.set_ylim(10, 12) to my code, one of the graph was disappered!

Answer 1

I think it does plot the black graph, but it's out of range. You can check that by adding 11 or something to the black plot value.
Maybe you can try using ax2.set_yticks(np.arange(-1, 1, 0.5)) instead of set_ylim and/or using ax2.autoscale(enable=True, axis=y)