Python - add colorbars in multiple plots for each plot

Question

I have multiple plots on a figure. I would like to add colorbars for each results. These colorbars must have the same height of my results and i would like to limit the numbers displayed on the colorbar to 3 values (in order to have readable figures).

My code is :

fig, axes = plt.subplots(nrows=1, ncols=3)

plt.tight_layout(pad=0.5, w_pad=2.5, h_pad=2.0)
ax1 = plt.subplot(131) # creates first axis
ax1.set_xticks([0,2000,500,1000,1500])
ax1.set_yticks([0,2000,500,1000,1500])
ax1.imshow(U,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
ax1.set_title("$ \mathrm{Ux_{mes} \/ (pix)}$")
ax2 = plt.subplot(132) # creates second axis
ax2.set_xticks([0,2000,500,1000,1500])
ax2.set_yticks([0,2000,500,1000,1500])
ax2.imshow(UU,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
ax2.set_title("$\mathrm{Ux_{cal} \/ (pix)}$")
ax3 = plt.subplot(133) # creates first axis
ax3.set_xticks([0,2000,500,1000,1500])
ax3.set_yticks([0,2000,500,1000,1500])
ax3.imshow(resU,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
ax3.set_title("$\mathrm{\mid Ux - Ux \mid \/ (pix)}$ ")
plt.show()

I try to add : "fig.colorbar(U, axes=ax1,fraction=0.046, pad=0.04)" but it doesnt work...

Answer 1

You can add a colorbar using plt.colorbar . It requires the image as an argument. In order to appear at the correct axes it also requires the axis to which it is attached

plt.tight_layout(pad=0.5, w_pad=2.5, h_pad=2.0)
ax1 = plt.subplot(131) # creates first axis
ax1.set_xticks([0,2000,500,1000,1500])
ax1.set_yticks([0,2000,500,1000,1500])
i1 = ax1.imshow(U,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
plt.colorbar(i1,ax=ax1,ticks=np.linspace(np.amin(U),np.amax(U),3))

ax1.set_title("$ \mathrm{Ux_{mes} \/ (pix)}$")
ax2 = plt.subplot(132) # creates second axis
ax2.set_xticks([0,2000,500,1000,1500])
ax2.set_yticks([0,2000,500,1000,1500])
i2=ax2.imshow(UU,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
ax2.set_title("$\mathrm{Ux_{cal} \/ (pix)}$")
plt.colorbar(i2,ax=ax2,ticks=np.linspace(np.amin(UU),np.amax(UU),3))

ax3 = plt.subplot(133) # creates first axis
ax3.set_xticks([0,2000,500,1000,1500])
ax3.set_yticks([0,2000,500,1000,1500])
i3 = ax3.imshow(resU,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
ax3.set_title("$\mathrm{\mid Ux - Ux \mid \/ (pix)}$ ")
plt.colorbar(i3,ax=ax3,ticks=np.linspace(np.amin(resU),np.amax(resU),3))

plt.show()

Update

If the colorbars height is too large you can solve that with

plt.colorbar(...,fraction=0.046, pad=0.04) 

as emphasized here

In case the plots overlap try

plt.gcf().tight_layout()

Answer 2

Following the answer to @plonser,

tick = np.linspace(min(your_variable),max(your_variable),3)

plt.tight_layout(pad=0.5, w_pad=2.5, h_pad=2.0)
ax1 = plt.subplot(131) # creates first axis
ax1.set_xticks([0,2000,500,1000,1500])
ax1.set_yticks([0,2000,500,1000,1500])
i1 = ax1.imshow(U,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
plt.colorbar(i1,ax=ax1,ticks=tick)

ax1.set_title("$ \mathrm{Ux_{mes} \/ (pix)}$")
ax2 = plt.subplot(132) # creates second axis
ax2.set_xticks([0,2000,500,1000,1500])
ax2.set_yticks([0,2000,500,1000,1500])
i2=ax2.imshow(UU,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
ax2.set_title("$\mathrm{Ux_{cal} \/ (pix)}$")
plt.colorbar(i2,ax=ax2,ticks=tick)

ax3 = plt.subplot(133) # creates first axis
ax3.set_xticks([0,2000,500,1000,1500])
ax3.set_yticks([0,2000,500,1000,1500])
i3 = ax3.imshow(resU,cmap='hot',extent=(X.min(),2000,Y.min(),2000))
ax3.set_title("$\mathrm{\mid Ux - Ux \mid \/ (pix)}$ ")
plt.colorbar(i3,ax=ax3,ticks=tick)

plt.show()

When you specify, you do so using ax=ax1 and not axes=ax1 . Also to limit the number of items in your colorbar , you can do so using the ticks option.