qqplot

hydrostats.visual.qqplot(merged_data_df=None, sim_array=None, obs_array=None, interpolate='linear', title=None, xlabel='Simulated Data Quantiles', ylabel='Observed Data Quantiles', legend=False, replace_nan=None, replace_inf=None, remove_neg=False, remove_zero=False, figsize=(12, 8))

Plots a Quantile-Quantile plot of the simulated and observed data.

Useful for comparing to see whether the two datasets come from the same distribution.

Parameters:
  • merged_data_df (DataFrame) – Dataframe must contain a datetime type index and floating point type numbers in two columns. The left column must be simulated data and the right column must be observed data. If given, sim_array and obs_array must be None.
  • sim_array (1D ndarray) – Array of simulated data. If given, merged_data_df parameter must be None and obs_array must be given.
  • obs_array (1D ndarray) – Array of observed data. If given, merged_data_df parameter must be None and sim_array must be given.
  • interpolate (str) – Specifies the interpolation type when computing quantiles.
  • title (str) – If given, sets the title of the plot.
  • xlabel (str) – The label for the x axis that holds the simulated data quantiles.
  • ylabel (str) – The label for the y axis that holds the observed data quantiles.
  • legend (bool) – If True, a legend to explain the elements on the plot will be added.
  • replace_nan (float, optional) – If given, indicates which value to replace NaN values with in the two arrays. If None, when a NaN value is found at the i-th position in the observed OR simulated array, the i-th value of the observed and simulated array are removed before the computation.
  • replace_inf (float, optional) – If given, indicates which value to replace Inf values with in the two arrays. If None, when an inf value is found at the i-th position in the observed OR simulated array, the i-th value of the observed and simulated array are removed before the computation.
  • remove_neg (boolean, optional) – If True, when a negative value is found at the i-th position in the observed OR simulated array, the i-th value of the observed AND simulated array are removed before the computation.
  • remove_zero (boolean, optional) – If true, when a zero value is found at the i-th position in the observed OR simulated array, the i-th value of the observed AND simulated array are removed before the computation.
  • figsize (tuple of float) – Tuple of length two that specifies the horizontal and vertical lengths of the plot in inches, respectively.
Returns:

fig – A matplotlib figure handle is returned, which can be viewed with the matplotlib.pyplot.show() command.
Return type:

Matplotlib figure instance

Examples

>>> import hydrostats.data as hd
>>> import hydrostats.visual as hv
>>> import matplotlib.pyplot as plt

>>> sfpt_url = r'https://github.com/waderoberts123/Hydrostats/raw/master/Sample_data/sfpt_data/magdalena-calamar_interim_data.csv'
>>> glofas_url = r'https://github.com/waderoberts123/Hydrostats/raw/master/Sample_data/GLOFAS_Data/magdalena-calamar_ECMWF_data.csv'
>>> merged_df = hd.merge_data(sfpt_url, glofas_url, column_names=('SFPT', 'GLOFAS'))

>>> qqplot(merged_data_df=merged_df, title='Quantile-Quantile Plot of Data',
>>>        xlabel='SFPT Data Quantiles', ylabel='GLOFAS Data Quantiles', legend=True,
>>>        figsize=(8, 6))
>>> plt.show()
../_images/qqplot.png