title: 'unable to find an inherited method for function ‘X’ for signature ‘"y"’
body: <p>While trying to interpolate using the idw function from R's gstat package an error keeps popping up. I got it running and fixed it somehow, but the error keeps popping up while changing small things. I might be able to solve it myself, once I understand what the error is. Can somebody elaborate on the following error?</p>
  
  <p>'unable to find an inherited method for function ‘X’ for signature ‘"y"’</p>
  
  <p>Thanks! </p>