Reprojecting unequal number of latitude and longitude: pyproj.exceptions.ProjError: x, y, z, and time must be same size

Question

I have a rectangular matrix of geographic climate data with a 1d row of latitude coordinates (size=834) and a 1d column with longitude coordinates (size=1115). They are both in unit of m (EPSG:32630) and I would like to transform to lat/lon. When I try to do:

    from pyproj import Proj, transform

    inProj = Proj('epsg:32630')
    outProj = Proj('epsg:4326')
    x1 = precip.lon.values
    x2 = precip.lat.values
    x2, y2 = transform(inProj, outProj, precip.lon.values, precip.lat.values)
    print (x2, y2)

I get the error:

Traceback (most recent call last):
  File "<input>", line 4, in <module>
  File "<conda_env>/lib/python3.7/site-packages/pyproj/transformer.py", line 759, in transform
    ).transform(xx=x, yy=y, zz=z, tt=tt, radians=radians, errcheck=errcheck)
  File "<conda_env>/lib/python3.7/site-packages/pyproj/transformer.py", line 446, in transform
    errcheck=errcheck,
  File "pyproj/_transformer.pyx", line 459, in pyproj._transformer._Transformer._transform
pyproj.exceptions.ProjError: x, y, z, and time must be same size

Does anyone know how I can transform from PCS to GCS with Python without having equal amount of latitude and longitude values?

Answer 1

Thanks to the comment from Martin, I did what he suggested first. I guess there is no way to just reproject latitude and longitude seperately and not if they are uneven.

    x1 = precip.lon.values
    y1 = precip.lat.values
    y1 = y1.reshape(-1,1)

#Generate two equal matrices with longitude and latitude.
    ones = np.ones((834,1115))
    xlon = np.multiply(ones, x1)
    ylat = np.multiply(ones, y1)
    lat, lon = transform(inProj, outProj, xlon, ylat)

This did solve my problem but I am still confused why it needs to be xlon, ylat, but this worked out and gave the right projection in the end. I tried first transform(inProj, outProj, ylat, xlon) but did not give any correct projection. If somebody knows what is going on I would like to know. I could not find any explanation in the docs.