smooth curve of scatter data frame data in R and add confedence interval
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I have many data.frame and each one contains many columns. Say my first data.frame col1=a, col2=b,col3=c

I want to plot x-axis=b/a  and y-xis=a. I managed to plot them (scatter plot) 

plot (dataframe$b/dataframe$a, dataframe$a, xlim=...,ylim=..) 

Now, I need to get the pattern for the scatter data ( I don't want linear regression as both of x and y are changing). I did use the command loess(..) and I was able to show the pattern.

lo_smooth<-loess(x,y, f=number, iter=number)


The question is how I can add the confidence intervals (CI) to the graph. In other words I want to check if two data.frame are within each other CI or not.

Thank you  