[Python] Calculate a monthly minimum, mean and maximum on daily temperature data for February...

I'm fairly new to Python and I'm trying to calculate the minimum, average and maximum monthly temperature from daily data for February.

I'm having a bit of trouble applying my code from other months to February.

Here is my code for the 31-day months :

import xarray as xr
import numpy as np
import copernicusmarine

DS = copernicusmarine.open_dataset(dataset_id="cmems_mod_glo_phy_my_0.083deg_P1D-m", minimum_longitude = -1.68, maximum_longitude = -1.56, minimum_latitude = 49.63, maximum_latitude = 49.67, minimum_depth = 0, maximum_depth = 0)
var_arr = np.zeros((341,len(DS['depth']),len(DS['latitude']),len(DS['longitude'])))

ind_time = -1
for y in range(2010,2021):
ind_time += 1
print(y)
start_rangedate = "%s"%y+"-01-01"
end_rangedate = "%s"%y+"-01-31"
subset_thetao = DS.thetao.sel(time = slice(start_rangedate, end_rangedate))
var_arr[31*ind_time:31*(ind_time+1),:,:,:] = subset_thetao.data
minimum = np.nanmin(var_arr)
print(minimum)
moyenne = np.mean(var_arr)
print(moyenne)
maximum = np.nanmax(var_arr)
print(maximum)

# 31 * 11 (years) = 341


It works well.

For February I first tried this :

DS = copernicusmarine.open_dataset(dataset_id="cmems_mod_glo_phy_my_0.083deg_P1D-m", minimum_longitude = -1.68, maximum_longitude = -1.56, minimum_latitude = 49.63, maximum_latitude = 49.67, minimum_depth = 0, maximum_depth = 0)
years_feb_28 = [2010,2011,2013,2014,2015,2017,2018,2019]
years_feb_29 = [2012,2016,2020]
var_arr = np.zeros((311,len(DS['depth']),len(DS['latitude']),len(DS['longitude'])))

ind_time_28 = -1
ind_time_29 = -1
for y in range(2010,2021):
print(y)
start_rangedate = "%s"%y+"-02-01"
if y in years_feb_28:
ind_time_28 += 1
end_rangedate = "%s"%y+"-02-28"
subset_thetao1 = DS.thetao.sel(time = slice(start_rangedate, end_rangedate))
var_arr[28*ind_time_28:28*(ind_time_28+1),:,:,:] = subset_thetao1.data
if y in years_feb_29:
ind_time_29 += 1
end_rangedate = "%s"%y+"-02-29"
subset_thetao2 = DS.thetao.sel(time = slice(start_rangedate, end_rangedate))
var_arr[29*ind_time_29:29*(ind_time_29+1),:,:,:] = subset_thetao2.data

minimum = np.nanmin(var_arr)
print(minimum)
maximum = np.nanmax(var_arr)
print(maximum)
moyenne = np.mean(var_arr)
print(moyenne)

# (8 x 28) + (3 x 29) = 311


It works, but the values seem wrong to me.

The result is :

minimum : 0.0
mean : 10.118808567523956
maximum :6.510576634161725


I tried with a single ind_time.

DS = copernicusmarine.open_dataset(dataset_id="cmems_mod_glo_phy_my_0.083deg_P1D-m", minimum_longitude = -1.68, maximum_longitude = -1.56, minimum_latitude = 49.63, maximum_latitude = 49.67, minimum_depth = 0, maximum_depth = 0)
years_feb_28 = [2010,2011,2013,2014,2015,2017,2018,2019]
years_feb_29 = [2012,2016,2020]
var_arr = np.zeros((311,len(DS['depth']),len(DS['latitude']),len(DS['longitude'])))

ind_time = -1
for y in range(2010,2021):
print(y)
start_rangedate = "%s"%y+"-02-01"
if y in years_feb_28:
ind_time += 1
end_rangedate = "%s"%y+"-02-28"
subset_thetao1 = DS.thetao.sel(time = slice(start_rangedate, end_rangedate))
var_arr[28*ind_time:28*(ind_time+1),:,:,:] = subset_thetao1.data
if y in years_feb_29:
ind_time += 1
end_rangedate = "%s"%y+"-02-29"
subset_thetao2 = DS.thetao.sel(time = slice(start_rangedate, end_rangedate))
var_arr[29*ind_time:29*(ind_time+1),:,:,:] = subset_thetao2.data

minimum = np.nanmin(var_arr)
print(minimum)
maximum = np.nanmax(var_arr)
print(maximum)
moyenne = np.mean(var_arr)
print(moyenne)


But I get this error message without understanding where the value 21 comes from :

Cell In[7], line 38
var_arr[29*ind_time:29*(ind_time+1),:,:,:] = subset_thetao2.data

ValueError: could not broadcast input array from shape (29,1,1,2) into shape (21,1,1,2)


Someone told me that the data taken into account may stop at year-02-28 T:00:00:00 (for 28-day years) and year-02-29 T:00:00:00 (for 29-day years) and that the code doesn't take the last day into account. So I tried to extend the end_rangedate to year-03-01 but I get this :

Cell In[8], line 33
var_arr[28*ind_time:28*(ind_time+1),:,:,:] = subset_thetao1.data

ValueError: could not broadcast input array from shape (29,1,1,2) into shape (28,1,1,2)


Could someone explain to me what I'm doing wrong ?

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