change orientation of contour clabel text objects

Question

I'm using Python Matplotlib to plot contours. Here's some code I have below as a basis. If you run this, you'll see that the labels are almost at vertical. I'd like to get the labels orientated horizontal, but I have no idea how can achieve this. I've tried with ClabelText, which the documentation suggests, but don't understand how this is supposed to work. I'd appreciate if someone could suggest a way to orientate the labels, either with or without ClabelText.

import itertools as it
import numpy as np
from matplotlib.ticker import FuncFormatter
from matplotlib.contour import ClabelText
import matplotlib.pyplot as plt
from math import pi, log 

def getTime(data):
    M = data['weight']
    Tei  = data['temp']
    Twasser = 99.8
    Teikl = 86.0  ## max allowed temp
    k = 0.262 ## estimate was 0.3 W/(m.K),
    Crho = 3.18 # (KJ/kgC)
    const = pow(Crho, 1.0/3) / (pi*pi*k*pow(4*pi/3,2.0/3))
    Tval = const*pow(M,2.0/3)*log(0.76*(Tei-Twasser)/(Teikl-Twasser))
    return Tval # coo time in minutes

def contourFmt(val, posn):
    mins = int(val // 1)
    secs = int(val % 1 *60)
    return '{0:d}mm{1:d}ss'.format(mins, secs)

def labeler(val): #is this any use??
    print(val)
    return

#weights = np.array(range(40, 80, 5))*1.0
#temps = np.array(range(0, 30, 5))*1.0
weights = np.arange(40.0, 80.0, 5.0)
temps = np.arange(0.0, 25.01, 5.0)

X = temps
Y = weights
Z = np.zeros((len(X), len(Y))) 
xx = [{'temp':i} for i in X]
yy = [{'weight':i} for i in Y]
plt.figure()

##zz = it.product(xx,yy)

for i, xdicts in enumerate(xx):
    for j, ydicts in enumerate(yy):
        zd = {}
        zd.update(xdicts)
        zd.update(ydicts)
        zval = getTime(zd)
        Z[i,j] = zval

times = np.arange(4.00, 6.50, 0.25)
CS = plt.contour(Y, X, Z, levels=times, colors='b')

lbl = ClabelText(labeler)
lbl.set_rotation('horizontal')
formatter = FuncFormatter(contourFmt)  
#plt.clabel(CS, inline=True, fmt=formatter, fontsize=12)
plt.clabel(CS, inline=True, use_clabeltext=True, fmt=formatter, fontsize=12)

plt.grid(True)
plt.clabel(CS, inline=1, fontsize=12)
plt.show()

Answer 1

You can set the rotation of the individual labels after they have been created. The label Text objects are returns by clabel, so you can store them and iterate over them, using .set_rotation(0) to orient them horizontally.

Change the last few lines of your script to:

labels1 = plt.clabel(CS, inline=True, use_clabeltext=True, fmt=formatter, fontsize=12)
labels2 = plt.clabel(CS, inline=1, fontsize=12)

for l in labels1+labels2:
    l.set_rotation(0)