I am attempting to use a scatter plot with a smooth line on the following data:

X Y2 Y1
21.0 2.2 2.2
21.1 1.5
21.2 1.3
21.3 1.3 1.6
21.4 1.9
21.5 1.8 2.1

The curve for Y2 data is correct.

However, I cannot get the curve for Y1 data to be correct.

If I specify the Y values for Y1 as a range e.g. $B$1:$B$6 then no plot is created at all. If I specify Y values as discrete points e.g. $B$1, $B$4, $B$6 a plot is created, but the position of the data point 1.3 is placed at 21.1 on the X-axis and data point 1.8 is positioned at 21.2 on the X-axis.

Any help will be much appreciated. TIA, Joe