diff --git a/R/buildNetwork.R b/R/buildNetwork.R
index 4d9eee0..ef32f53 100644
--- a/R/buildNetwork.R
+++ b/R/buildNetwork.R
@@ -71,8 +71,8 @@ defineEIC <- function(xdata) {
         ncol = length(rts.xdata))
     for( i in seq_len(nrow(peaks)) ){
         peak <- peaks[i,]
-        posrtmin <- which(rts.xdata == peak["rtmin"])
-        posrtmax <- which(rts.xdata == peak["rtmax"])
+        posrtmin <- which.min(abs(rts.xdata - peak["rtmin"]))
+        posrtmax <- which.min(abs(rts.xdata - peak["rtmax"]))
         rangepeak <- seq(posrtmin, posrtmax, by = 1)
         peakint <- unlist(lapply(rangepeak,function(y) {
             mzposc <- which(mzs.xdata[[y]] >= peak["mzmin"])
diff --git a/R/findIsotopes.R b/R/findIsotopes.R
index a84ec58..86f6464 100644
--- a/R/findIsotopes.R
+++ b/R/findIsotopes.R
@@ -243,7 +243,7 @@ getIsotopes <- function(anclique, maxCharge = 3,
     ## If there are no isotopes in all dataset
     if( length(listofisoTable) ==
         sum(vapply(listofisoTable, is.null, logical(1))) ) {
-            isoTable <- matrix(c(NA,NA,NA,NA), nrow = 1)
+            isoTable <- as.data.frame(matrix(c(NA,NA,NA,NA), nrow = 1))
             colnames(isoTable) <- c("feature","charge","grade","cluster")
             anclique@peaklist$isotope <- rep("M0", nrow(anclique@peaklist))
     } else {
@@ -252,9 +252,11 @@ getIsotopes <- function(anclique, maxCharge = 3,
         listofisoTable <- listofisoTable[
             !vapply(listofisoTable, is.null, logical(1))]
         maxC <- max(listofisoTable[[1]]$cluster)
-        for(i in 2:length(listofisoTable)) {
-            listofisoTable[[i]]$cluster = listofisoTable[[i]]$cluster + maxC + 1
-            maxC <- max(listofisoTable[[i]]$cluster)
+        if (length(listofisoTable) > 1) {
+            for(i in 2:length(listofisoTable)) {
+                listofisoTable[[i]]$cluster = listofisoTable[[i]]$cluster + maxC + 1
+                maxC <- max(listofisoTable[[i]]$cluster)
+            }
         }
         isoTable <- do.call(rbind, listofisoTable)
         rownames(isoTable) <- seq_len(nrow(isoTable))