topic Re: Missing Observations in Zonal Statistics Tool in Data Management Questions

Missing Observations in Zonal Statistics Tool

GwanSeonKim — Thu, 17 Nov 2016 19:21:03 GMT

Hi,

I am using zonal statistical fools and I would like to ask you one question that I have.

I have field boundary shpefile which has 1062063 observations. I am using zonal statistical as table tool to obtain

slope values from raster layer. when I run the tool, I only have 1003273 observations.

I guess there are 58790 missing observations. Do you have any ideas why there are missing observations and how I can fix these missing observations?

Thank you.

Re: Missing Observations in Zonal Statistics Tool

NeilAyres — Thu, 17 Nov 2016 19:54:18 GMT

Well the whole idea of zonal statistics is to aggregate or summarise a variable within spatial zones.

So why should you have a zonal file with exactly the same number of records as your data?

What are you trying to achieve here?

Re: Missing Observations in Zonal Statistics Tool

GwanSeonKim — Thu, 17 Nov 2016 20:08:43 GMT

Thanks for your response.

I have field boundaries in KY, and I have to get values such as slope and precipitation for each field.

Eventually, I want to make field-based panel data rather than county-based panel.

In each field, I can see what crop is grown, then estimate impact of precipitation on probability of crop rotation.

If zonal statistics tool provides less observations than original observations in shapefile, I will have missing field boundaries (missing observations).

It might result in sample selection bias in my estimation.

That's why I want to keep and match same number of records as my original shapefile.

Re: Missing Observations in Zonal Statistics Tool

NeilAyres — Fri, 18 Nov 2016 06:58:43 GMT

But if "That's why I want to keep and match same number of records as my original shapefile."

Then you are not achieving anything by using zonal statistics. The original data is the same as the "summary".