RobbieC
Active Member
 Joined
 Dec 14, 2016
 Messages
 376
 Office Version

 2010
 Platform

 Windows
Hi there, I have a spreadsheet where I am entering reading from a soakaway test (to see how long water drains in a hole in the ground)
I have a table where I record my readings over time (I just record the depth in m):
From this data I can produce this graph:
So the blue line represents the readings that I have taken. The graph also shows the green lines which represent the 25% & 75% points of the test.
What I need to do is to calculate at what time (mins) the soakaway hits the 25% & 75% marks.
In this example, the 75% is 0.75*2 (2 being the total depth) which is 1.5. This happens to be one of the readings taken so in this example it's pretty easy to calculate (45 mins)
But the 25% mark is crossed without an exact reading, so I need to calculate the exact time the curve of the graph passes that point (somewhere around 12.5 mins)
Obviously, automating both of theses graphcrossing points to get the exact values is the aim of the exercise. Trouble is, I have no idea how to do this... must be a formula to extrapolate or something....
If you can possibly point me in the right direction, I'd be very grateful. It has been a journey to get this far and to get those 2 values would be the cherry on the cake
Thanks very much
Rob
I have a table where I record my readings over time (I just record the depth in m):
From this data I can produce this graph:
So the blue line represents the readings that I have taken. The graph also shows the green lines which represent the 25% & 75% points of the test.
What I need to do is to calculate at what time (mins) the soakaway hits the 25% & 75% marks.
In this example, the 75% is 0.75*2 (2 being the total depth) which is 1.5. This happens to be one of the readings taken so in this example it's pretty easy to calculate (45 mins)
But the 25% mark is crossed without an exact reading, so I need to calculate the exact time the curve of the graph passes that point (somewhere around 12.5 mins)
Obviously, automating both of theses graphcrossing points to get the exact values is the aim of the exercise. Trouble is, I have no idea how to do this... must be a formula to extrapolate or something....
If you can possibly point me in the right direction, I'd be very grateful. It has been a journey to get this far and to get those 2 values would be the cherry on the cake
Thanks very much
Rob