1 files changed, 3 insertions, 1 deletions
diff --git a/R/tf.R b/R/tf.R
index 135a2d7..f811b6c 100644
--- a/R/tf.R
+++ b/R/tf.R
@@ -1,6 +1,8 @@
 # S3 class for defining trasnfer functions
 tf <- function(num=c(1),den=c(1),Ts=1){
-  
+  out <- list(num=num,den=den,Ts=Ts)
+  class(out) <- "tf"
+  return(out)
 }
 
 # Display the Transfer Function