Matplotlib Specify format of floats for tick labels

Question

I am trying to set the format to two decimal numbers in a matplotlib subplot environment  Unfortunately  I do not have any idea how to solve this task   To prevent using scientific notation on the y-axis I used ScalarFormatter useOffset False  as you can see in my snippet below  I think my task should be solved by passing further options arguments to the used formatter  However  I could not find any hint in matplotlib s documentation   How can I set two decimal digits or none  both cases are needed   I am not able to provide sample data  unfortunately     -- SNIPPET --  f  axarr   plt subplots 3  sharex True   data   conv air x   range 0  len data    axarr 0  scatter x  data  axarr 0  set ylabel   T  mathrm air 2 2     size FONT SIZE  axarr 0  yaxis set major locator MaxNLocator 5   axarr 0  yaxis set major formatter ScalarFormatter useOffset False   axarr 0  tick params direction  out   labelsize FONT SIZE  axarr 0  grid which  major   alpha 0 5  axarr 0  grid which  minor   alpha 0 2   data   conv dryer x   range 0  len data    axarr 1  scatter x  data  axarr 1  set ylabel   T  mathrm dryer 2 2     size FONT SIZE  axarr 1  yaxis set major locator MaxNLocator 5   axarr 1  yaxis set major formatter ScalarFormatter useOffset False   axarr 1  tick params direction  out   labelsize FONT SIZE  axarr 1  grid which  major   alpha 0 5  axarr 1  grid which  minor   alpha 0 2   data   conv lambda x   range 0  len data    axarr 2  scatter x  data  axarr 2  set xlabel  Iterationsschritte   size FONT SIZE  axarr 2  xaxis set major locator MaxNLocator integer True   axarr 2  set ylabel    lambda    size FONT SIZE  axarr 2  yaxis set major formatter ScalarFormatter useOffset False   axarr 2  yaxis set major locator MaxNLocator 5   axarr 2  tick params direction  out   labelsize FONT SIZE  axarr 2  grid which  major   alpha 0 5  axarr 2  grid which  minor   alpha 0 2

User · Answer

format labels using lambda function

3x the same plot with differnt y-labeling

Minimal example

import numpy as np
import matplotlib as mpl
import matplotlib.pylab as plt
from matplotlib.ticker import FormatStrFormatter

fig, axs = mpl.pylab.subplots(1, 3)

xs = np.arange(10)
ys = 1 + xs ** 2 * 1e-3

axs[0].set_title('default y-labeling')
axs[0].scatter(xs, ys)
axs[1].set_title('custom y-labeling')
axs[1].scatter(xs, ys)
axs[2].set_title('x, pos arguments')
axs[2].scatter(xs, ys)


fmt = lambda x, pos: '1+ {:.0f}e-3'.format((x-1)*1e3, pos)
axs[1].yaxis.set_major_formatter(mpl.ticker.FuncFormatter(fmt))

fmt = lambda x, pos: 'x={:f}\npos={:f}'.format(x, pos)
axs[2].yaxis.set_major_formatter(mpl.ticker.FuncFormatter(fmt))

You can also use 'real'-functions instead of lambdas, of course. https://matplotlib.org/3.1.1/gallery/ticks_and_spines/tick-formatters.html

User · Answer

If you are directly working with matplotlib s pyplot  plt  and if you are more familiar with the new-style format string  you can try this   from matplotlib ticker import StrMethodFormatter plt gca   yaxis set major formatter StrMethodFormatter   x   0f       No decimal places plt gca   yaxis set major formatter StrMethodFormatter   x   2f       2 decimal places   From the documentation      class matplotlib ticker StrMethodFormatter fmt        Use a new-style format string  as used by str format    to format the   tick       The field used for the value must be labeled x and the field used for   the position must be labeled pos

User · Answer

The answer above is probably the correct way to do it  but didn t work for me    The hacky way that solved it for me was the following    ax    lt whatever your plot is gt     get the current labels  labels    item get text   for item in ax get xticklabels      Beat them into submission and set them back again ax set xticklabels  str round float label   2   for label in labels     Show the plot  and go home to family  plt show

User · Answer

In matplotlib 3 1  you can also use ticklabel format  To prevents scientific notation without offsets   plt gca   ticklabel format axis  both   style  plain   useOffset False

User · Answer

See the relevant documentation in general and specifically  from matplotlib ticker import FormatStrFormatter  fig  ax   plt subplots    ax yaxis set major formatter FormatStrFormatter    2f

[python] Matplotlib: Specify format of floats for tick labels

format labels using lambda function

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