First commit with the code Hector shared with me

10_EXPORTS/lag_apply.R

@@ -0,0 +1,26 @@
+# rolling 
+
+  # x = vector of values
+  # n = window size
+  # callback = function target, in the format "function(x){sd(x)}" or "function(x){mean(x)}"
+
+
+'# 04 / 11 /2025
+
+ℹ In group 1: `uniqueID = "PYR11_BASE_01"`.
+Caused by error in `x[i:(i + n - 1)]`:
+! only 0s may be mixed with negative subscripts
+
+Added: '
+
+
+lag_apply <- function(x, n, callback){
+  k = length(x);
+  result = rep(NA, k);
+  for(i in 1 : (k - n + 1)){ # 1 : (k - n + 1)
+    result[i+(n-1)] <- callback(x[i:(i + n-1)]);
+  }    
+  return(result);
+}
+
+# lag_apply(subset(mean_stand_export_list, PLOT == "PYR00")$nTrees.ha, 20, function(x){mean(x)})