---
title: "Aggregation levels on calc"
url: "https://openforis.support/questions/175/aggregation-levels-on-calc"
tags: ["calc"]
status: "answered"
score: 0
answer_count: 1
asked: "2015-02-10T13:55:37"
last_activity: "2015-02-10T17:56:47"
source: "Open Foris Support - Q&A Forum"
license: "Copyright Open Foris, 2021. Some rights reserved under creative commons license."
---

# Aggregation levels on calc

Asked by PekkaH on 2015-02-10

Hey,
I have sample plots divided on stands (=plot sections) on my data. That means that trees (and other data also) are recorded by stands. How do I aggregate my data? If I use point estimator (error estimates), I should aggregate by stands, correct? If so, should I have columns ""cluster", "plot", "stand", "aoi_code" in "Sampling unit table" (One-phase sampling) and "stand" as "Sampling unit"?

Cheers,
Pekka


## Answer (score 0, by Mino Togna on 2015-02-10)

Link: https://openforis.support/questions/175/aggregation-levels-on-calc/178

Hello Pekka,

Yes, in this context, the entity stand is the sampling unit to select in Calc and it must have the column cluster, in case it's cluster sampling and it must have a variable used to match with AOI csv file you upload (e.g. aoi_code).

Keep in mind, when assigning the weight to the sampling unit (stand), to assign 1 only to center stands for the correct calculation of the expansion factor.

Please let me know if you have further questions.
Thank you
Mino