title: Metafor Error in escalc One or more sample sizes are < 1
body: <p>My metafor code in R used to run with the 0 occurrences of means in some of the papers but now it shows an error: Metafor Error in escalc One or more sample sizes are &lt; 1</p>
  <p>This is the code:
  Error in escalc(measure = &quot;MN&quot;, mi = mean_identity_exp, sdi = SD_identity_exp, : One or more sample sizes are &lt; 1</p>
  <p>Should I use the drop00 to tell it to mark the 0s are NAs? It used to do that automatically in the past; I don't know if it was updated. how should I write the code to make it run regardless of the 00s and what are the implications?</p>