绘制数据框的轮廓图，x 轴作为日期时间，y 轴作为深度

Question

I have a dataframe with the indexes as datetime and columns as depths. I would like to plot a contour plot which looks something like the image below. Any ideas how I should go about doing this? I tried using the plt.contour() function but I think I have to sort out the arrays for the data first. I am unsure about this part.

Example of my dataframe:

Datetime             -1.62  -2.12  -2.62  -3.12  -3.62  -4.12  -4.62  -5.12                                                        
2019-05-24 15:45:00   4.61   5.67   4.86   3.91   3.35   3.07   3.03   2.84   
2019-05-24 15:50:00   3.76   4.82   4.13   3.32   2.84   2.40   2.18   1.89   
2019-05-24 15:55:00   3.07   3.77   3.23   2.82   2.41   2.21   1.93   1.81   
2019-05-24 16:00:00   2.50   2.95   2.63   2.29   1.97   1.73   1.57   1.48   
2019-05-24 16:05:00   2.94   3.62   3.23   2.82   2.62   2.31   2.01   1.81   
2019-05-24 16:10:00   3.07   3.77   3.23   2.82   2.51   2.31   2.10   1.89   
2019-05-24 16:15:00   2.71   3.20   2.86   2.70   2.51   2.31   2.18   1.97   
2019-05-24 16:20:00   2.50   3.07   2.86   2.82   2.73   2.50   2.37   2.22   
2019-05-24 16:25:00   2.40   3.20   3.10   2.93   2.73   2.50   2.57   2.84   
2019-05-24 16:30:00   2.21   2.95   2.86   2.70   2.73   2.72   2.91   3.49   
2019-05-24 16:35:00   2.04   2.72   2.63   2.59   2.62   2.72   3.03   3.35   
2019-05-24 16:40:00   1.73   2.31   2.33   2.39   2.62   2.95   3.57

Example of the plot I want:

For the XYZ input in plt.contour() , I would like to find out what structure of data it requires. It says it requires a 2D array structure, but I am confused. How do I get that with my current dataframe?

Answer 1

I have worked out a solution. Note that the X (tt2) - time input, and Y(depth) - depth input, have to match the Z(mat2) matrix dimensions for the plt.contourf to work. I realised plt.contourf produces the image i want rather than plt.contour, which only plots the contour lines.

Example of my code:

tt2 = [...]
depth = [...]   
plt.title('SSC Contour Plot')
fig=plt.contourf(tt2,depth,mat2,cmap='jet',levels= 
[0,2,4,6,8,10,12,14,16,18,20,22,24,26], extend= "both")
plt.gca().invert_yaxis() #to flip the depth from shallowest to deepest
plt.gca().xaxis.set_major_formatter(mdates.DateFormatter('%d/%m/%Y %H:%M:%S'))
#plt.gca().xticklabels(tt)
cbar = plt.colorbar()
cbar.set_label("mg/l")
yy = len(colls2)
plt.ylim(yy-15,0) #assumming last 10 depth readings have NaN
plt.xlabel("Datetime")
plt.xticks(rotation=45)
plt.ylabel("Depth (m)")
plt.savefig(path+'SSC contour plot.png') #save plot 
plt.show()

Example of plot produced