v.qcount(1grass)

📦
version 8.5.0 · 10 versions
, in alpine 3.24, ubuntu stonking

💖 v.qcount — the manual, but make it make sense 💖

okay bestie, welcome to the GRASS User's Manual page for v.qcount ✨ this is v.qcount(1grass) and she is HERE to count quadrats for u 💅

🌸 NAME 🌸

v.qcount — Indices for quadrat counts of vector point lists. that's it, that's the vibe ✨

👑 KEYWORDS 👑

vector, statistics, point pattern 🎀

✨ SYNOPSIS ✨

v.qcount
v.qcount --help
v.qcount [-g] input=name  [layer=string]   [output=name]
nquadrats=integer radius=float  [--overwrite]  [--help]  [--verbose]
[--quiet]  [--ui]

🦋 Flags 🦋

  • -g — Print results in shell script style. that's it. script-y output, iconic behavior 💅
  • --overwrite — Allow output files to overwrite existing files. she will absolutely stomp on what's already there, so like, consent first 🙈
  • --help — Print usage summary. ur girl will explain herself 💖
  • --verbose — Verbose module output. she will overshare. love that for her 🌸
  • --quiet — Quiet module output. she will not. also love that for her 🤫
  • --ui — Force launching GUI dialog. clicks instead of typing, no cap ✨

🎀 Parameters 🎀

  • input=name [required] — Name of input vector map. Or data source for direct OGR access. so either a map or a direct OGR source, ur call bestie 🫶
  • layer=string — Layer number or name (-1 for all layers). A single vector map can be connected to multiple database tables. This number determines which table to use. When used with direct OGR access this is the layer name. Default: -1. so if u want EVERYTHING, u hit her with the -1 💅
  • output=name — Name for output quadrat centers map (number of points is written as category). yes the count is chillin' in the category, not an attribute table, remember that 💜
  • nquadrats=integer [required] — Number of quadrats. how many circles r we making, bestie 🌈
  • radius=float [required] — Quadrat radius. the size of each lil circle ⭐

🧚 DESCRIPTION 🧚

so v.qcount computes six different quadrat count statistics that provide a measure of how much an user defined point pattern departs from a complete spatial random point pattern. six!! she's doing SIX 💅

Points are distributed following a complete spatial randomness (CSR) pattern if events are equally likely to occur anywhere within an area. There are two types departure from a CSR: regularity and clustering. Figure 1 gives an example of a complete random, regular and a clustered pattern. 🦋

Figure 1: Realization of two-dimensional Poisson processes of 50 points on the unit square exhibiting (a) complete spatial randomness, (b) regularity, and (c) clustering.

Various indices and statistics measure departure from CSR. The v.qcount function implements six different quadrat count indices that are described in Cressie (1991; p. 590-591)<sup>[1]</sup> and in Ripley (1981; p. 102-106)<sup>[2]</sup> and summarized in Table 1. 📊

Table 1: Indices for Quadrat Count Data. Adapted from Cressie [1], this table shows the statistics computed for the quadrats in Figure 2.

These indices are computed as follows: v.qcount chooses nquadrads circular quadrats of radius radius such that they are completely within the bounds of the current region and no two quadrats overlap. The number of points falling within each quadrat are counted and indices are calculated to estimate the departure of point locations from complete spatial randomness. This is illustrated in Figure 2. 🔥

Figure 2: Randomly placed quadrats (n = 100) with 584 sample points.

The number of points is written as category to the output map (and not to an attribute table). ok say it with me: category, NOT attribute table. periodt. 💖

🎀 NOTES 🎀

This program may not work properly with lat-long data. It uses hypot() in two files: count.c and findquads.c. so like... be aware bestie 😭

💀 KNOWN ISSUES 💀

Timestamp not working for header part of counts output. (2000-10-28) — yeah she's been like this a while 🙈

🌈 REFERENCES 🌈

General references include:

  • [1] Noel A. C. Cressie. Statistics for Spatial Data. Wiley Series in Probability and Mathematical Statistics. John Wiley & Sons, New York, NY, 1st edition, 1991.
  • [2] Brian D. Ripley. Spatial Statistics. John Wiley & Sons, New York, NY, 1981.

References to the indices include:

  • [3] R. A. Fisher, H. G. Thornton, and W. A. Mackenzie. The accuracy of the plating method of estimating the density of bacterial populations. Annals of Applied Biology, 9:325-359, 1922.
  • [4] F. N. David and P. G. Moore. Notes on contagious distributions in plant populations. Annals of Botany, 18:47-53, 1954.
  • [5] J. B. Douglas. Clustering and aggregation. Sankhya B, 37:398-417, 1975.
  • [6] M. Lloyd. Mean crowding. Journal of Animal Ecology, 36:1-30, 1967.
  • [7] M. Morista. Measuring the dispersion and analysis of distribution patterns. Memoires of the Faculty of Science, Kyushu University, Series E. Biology, 2:215-235, 1959.

A more detailed background is given in the tutorial:

  • [8] James Darrell McCauley 1993. Complete Spatial Randomness and Quadrat Methods - GRASS Tutorial on v.qcount

👑 SEE ALSO 👑

v.random, v.distance, v.neighbors, v.perturb — go read those too, they're all iconic in their own way ✨

💜 AUTHORS 💜

James Darrell McCauley when he was at: Agricultural Engineering Purdue University

Modified for GRASS 5.0 by Eric G. Miller (2000-10-28) Modified for GRASS 5.7 by R. Blazek (2004-10-14)

🫶 SOURCE CODE 🫶

Available at: v.qcount source code (history)

Latest change: Tuesday Feb 25 14:08:58 2025 in commit: 429a8843c38637325f11575789155d5888d03270

Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

© 2003-2026 GRASS Development Team, GRASS 8.5.0 Reference Manual

ok that's the whole page bestie, every flag, every reference, every date, all of it, no crumbs left 💅 this was v.qcount from GRASS 8.5.0, page date stamped at the bottom of the original as GRASS 8.5.0 / v.qcount(1grass) — go forth and count ur quadrats, u ate that 🎀✨💖

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