## Dynamic identification of value on the curve

Hi,

I am trying to find a way to identify value of a point on curve intersected by line from x-axis. I am trying to overlay a series plot and needle plot. I know the value on x-axis for needle plot but would like to know corresponding value ( at the intersection point on seriesplot) on the curve and would like to display or extend the needle to that point ( i am uanble to figure out how to use TIP). I am using proc template with GTL code.

Any help is appreciated.

Thanks.

Vijay

1 ACCEPTED SOLUTION

Accepted Solutions  Jay54
Meteorite | Level 14

## Re: Dynamic identification of value on the curve

Not sure what you mean by "Dynamic".  Assuming you are not using the SMOOTHCONNECT option, the (x, y) points on a SERIESPLOT are connected with a straight line segments.  Assuming your data is sorted by the x variable, you can find the two points on the series that straddle the needle x-axis value.  Then, you can compute the y coordinate with a linear interpolation.  You could use a DROPLINE statement to create a "needle" from the intersection point to the x-axis.

4 REPLIES 4  Jay54
Meteorite | Level 14

## Re: Dynamic identification of value on the curve

Not sure what you mean by "Dynamic".  Assuming you are not using the SMOOTHCONNECT option, the (x, y) points on a SERIESPLOT are connected with a straight line segments.  Assuming your data is sorted by the x variable, you can find the two points on the series that straddle the needle x-axis value.  Then, you can compute the y coordinate with a linear interpolation.  You could use a DROPLINE statement to create a "needle" from the intersection point to the x-axis.

## Re: Dynamic identification of value on the curve

Thanks Sanjay for your quick response. I can give bit more details. I am plotting Hemoglin values versus drug exposure duration. I would like to check value of hemoglobin at a specific timepoint ( hemoglobin may not be collected at this point).

But this is an event date and i would like to see what would be hemoglobin value this this event time ( and draw needle from x-axis to this point).

Thanks.

Vijay

## Re: Dynamic identification of value on the curve

Is it appropriate to assume a linear interpolation between actual measurement times? If not you may want to look at a modeling procedure as the results would yeild an equation amenable to such graphing by building a display set.

## Re: Dynamic identification of value on the curve

Thanks both for response. I have used PROC TRANSREG to get the value for specific timepoint on x-axis. I got the answer i was looking for.

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