Here is a puzzle that I've worked a

[Drew08]

Here is a puzzle that I've worked at for a while with out much result. Take profile station-elevation data, in this case stream profile data cut from a less than perfect LiDAR source, and filter the data such that only local minimum ordinances are left resulting in a station-elevation series that "drapes" on the minimum values. See the example attached. In this case the original data is plotted in blue, and I want to filter the data to result in something that resembles the red line. Any thoughts?

 

[SkipVought]

Best I can do, added a 'Test' column...
[tt]
D95: =MIN($C$2:C94,$D$294)
[/tt]
...and copy/paste to end of table.

Series 2 Green line


Skip,

_{Just traded in my OLD subtlety...
for a NUance!}

 

[JG2828]

Skip's test column came up blank for me, but the line was there. Our lines look very similar.
I also added an additional column but used the IF function =IF(C4<D3,C4,D3) and copied down

 

[SkipVought]

@JG, only blank for the first 94 rows.

Skip,

_{Just traded in my OLD subtlety...
for a NUance!}

 

[JG2828]

skip, ok I see now. I was wondering why the line still showed up with no data there

 

[SkipVought]

OPs red line seemed to start around 620, hence the empty cells.

Skip,

_{Just traded in my OLD subtlety...
for a NUance!}

 

[IDS]

Skip - What is the second range in the Min function for? =MIN($C$2:C94) seems to give the same (or almost same) results.

JG - Your formula and Skip's work with descending data, but if the line starts to rise they will both return a horizontal line at the minimum value.

If you use =MIN($C2:C94) (remove the $ before the 2) the line will give the minimum over a range of 93 rows, so the line will rise if the data starts to rise, but with your data that range is too small, and gives a very jagged line. Extending the line to 200 rows seems to give reasonable results.

You could also add another column with a moving average which will smooth out the steps:
In Column D, starting at row 202: =Min(C2:C201)
In Column E, starting at row 302: =Average(D202401)

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/