fix #222 (#223)

Author: chainsawriot

.github/workflows/R-CMD-check.yaml

@@ -22,7 +22,7 @@ jobs:
         config:
           - {os: macos-latest,   r: 'release'}
           - {os: windows-latest, r: 'release'}
-          - {os: ubuntu-latest, r: '4.0'} ## minimum version
+          - {os: ubuntu-latest,   r: 'oldrel-4'} ## minimum version
           - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
           - {os: ubuntu-latest,   r: 'release'}
           - {os: ubuntu-latest,   r: 'oldrel-1'}

DESCRIPTION

@@ -49,5 +49,5 @@ Roxygen: list(markdown = TRUE)
 Encoding: UTF-8
 VignetteBuilder: knitr
 Depends: 
-    R (>= 4.0)
+    R (>= 4.1)
 Language: en-GB