Collecting and analyzing numerical data or making numerical summaries of data.

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18
votes
3answers
699 views

Major bug in ArcGIS Zonal statistics?

Update: The bug has been fixed in the ArcGIS 10.4 release I am using ArcGIS 10.2.2 to determine zonal statistics for a number of zones. If there is any NoData in the value raster, I want the zone ...
13
votes
6answers
5k views

Get Raster Values from a Polygon Overlay in Opensource GIS Solutions

I have two layers. A polygon-shape-layer with many tiles and a raster-layer containing CORINE 2006 land cover with many categories in a colourmap. I want to obtain for each polygon in the shapelayer a ...
12
votes
5answers
2k views

Determining min and max values in an ASCII raster dataset using Python?

I have a raster dataset in ASCII format. Using Python, I need to determine the min and max values inside the dataset. I've been told that the header information is key, which contains things like ...
12
votes
4answers
638 views

How is margin of error reported on a map?

When reporting estimates you should always include the margin of error. There are conventional ways of reporting margin of error in a table, text or graph. But, how do you report margin of error for ...
11
votes
2answers
3k views

How to calculate average slope in a grid?

This is actually a two part question: Which methods are there to calculate average slope by unit (say km²) for a given area? Are there any special requirements on the data - like additional ...
11
votes
4answers
594 views

Math and Stat for GIS and Computing

I am planning to do an advanced program in spatial science and engineering. It states as a requirement in the program, that the student should have a through understanding in math and statistics. So ...
9
votes
5answers
12k views

How to calculate raster statistics for polygons?

how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first. There is a way to ...
9
votes
1answer
351 views

Calculating spatial correlation between features from two separate layers in QGIS

I am trying to determine whether the presence of large numbers of active duty military troops in an area is spatially correlated with higher/lower levels of violent crime. That is, are the areas ...
8
votes
1answer
5k views

Getting tabular statistics from table using QGIS?

Are there QGIS tools that will allow users to get tabular statistics from their table? I kind of expected I would be able to just open the table, select the field I was interested in, right-click on ...
8
votes
2answers
651 views

How can I find the median column in a database?

I have data on period of construction for dwellings in dissemination areas. I have transferred this data to my study areas and would like to determine the median period of construction for each study ...
8
votes
2answers
7k views

Calculate area of intersecting polygons in QGIS

I have two collections of shapefiles: 1 - postal codes, administrative and political areas 2 - various land use categories like parks & allotments, and points like trees I want to produce ...
8
votes
3answers
269 views

spatial and spatiotemporal analyses

I have a dataset that consists of 247 mosquito traps placed in fixed positions and sampled weekly for 23 weeks. I also have dengue disease incidence data (indexed to home address) during the same time ...
7
votes
2answers
4k views

Frequency, summarize tool options of ArcGIS for Desktop?

I'm looking for some general frequency, summarize tool. What I basically want is some tool like the summarize tool in ArcGIS (right click in the attribute table> summarize) that runs on all attributes ...
7
votes
1answer
3k views

How to get GDAL to create statistics for GTiff in Python

I regularly create my own GeoTIFF rasters with GDAL in Python, e.g.: from osgeo import gdal from numpy import random data = random.uniform(0, 10, (300, 200)) driver = gdal.GetDriverByName('GTiff') ds ...
7
votes
2answers
118 views

How to automatically sum up values within buffers?

I want to establish the population figures within multi-ring buffers around certain site. I have set up the buffers and am running a select by location query on each concentric ring. Once the ...
7
votes
3answers
660 views

How to use ZonalStats plugin?

I am using QGIS 1.8.0 on a Windows Home Premium 7 machine. I have a single band TIFF that is 187 MB in size. My vector polygon shapefile represents a regular grid of a 147x112 36kmx36km grid cells. ...
7
votes
1answer
301 views

Graphically depict statistical difference between thematic rasters

The graph shows a regression between two raster datasets with classified tree canopy cover: class 1 = 0-10%, class 2 = 10 - 20% ...class 6 = >60% (Figure 1, Figure 2). The spatial resolution for ...
6
votes
1answer
1k views

Explaining different Standard Deviation results from same data in ArcGIS Desktop and MS Excel?

I have done some interpolation in Geostatistical Analyst in ArcGIS and I got the Standard Deviation (SD) a bit different from the SD that I calculated in Excel Spreadsheet. What algorithm does each ...
6
votes
2answers
2k views

Is it possible to access ArcGIS's table operations “Summarize…” and “Statistics…” in python?

ArcGIS has a few nifty table tools, including Summarize and Statistics. Is there a way to access them through arcpy, or will I have to hack my own methods via math and lists?
6
votes
3answers
518 views

Is it possible to calculate statistics across multiple fields in arcpy?

The summary statistics command can be used in arcpy to calculate statistics - this tool runs against a single field, eg: SUM—Adds the total value for the specified field. Is there an ...
6
votes
4answers
3k views

How to sum up pixel values in QGIS?

I need to know the value of the sum of all pixels in a raster. However, in the Statistics section of the Metadata tab in Properties, under Sum of All Cells it always indicates 0.00. I have tried with ...
6
votes
1answer
124 views

How can I generate a range of pantones for a map?

When I am given a map (or make one...) I often like to get an idea of the range of colours present. One thing this does is it allows me to quickly visualize contrast (helps build maps for colour blind ...
6
votes
1answer
2k views

ArcGIS median value from layer?

I've been hunting around ArcGIS 9.3 and having no success at finding a tool/function that can give me the median (not the mean/avg) tabular value of a spatial database. For example, if I have a data ...
5
votes
1answer
4k views

Recording frequency of names in the attribute table?

I have a question with ArcGIS 9.2. In an attribute table the column [name] includes the name of every place in this layer. Next to that (in columns [numbers]) there should be recorded how often a ...
5
votes
2answers
4k views

Is there a zonal statistics tool to calculate median and mode raster values for each polygon?

I'd like to calculate zonal statistics for a raster where the zones are defined by polygons in a vector layer within QGIS. Specifically I'm interested in calculating the median and mode raster values ...
5
votes
1answer
2k views

How to Group By with Summarize on alphanumeric field in ArcGIS Desktop?

Is it possible to create from Summarize option, a new table with the COUNT of a string field and the code of municipalities, in my case, like that: +-------------------+--------------+ | ...
5
votes
1answer
326 views

Why covariance values are different in R and ArcGIS?

I've calculated covariance between 7 rasters using R and ArcGIS. It gives me different results. Each times covariance values from R are approximately 1.874 times higher than ArcGIS values. R - ...
5
votes
1answer
740 views

Calculating Percentiles in ArcMap?

I have a large polygon dataset (26,000) records with numerous attributes columns. I wish to calculate the percentile rank of each attribute. Say I have population_density in an attribute, is there a ...
5
votes
2answers
2k views

Zonal statistics for millions of overlapping polygons

I am running ArcGIS 10.1 with 64-bit GP on Windows 8.1 x64. I want to calculate the zonal statistics of buffer polygons based on parcels and a kernel density raster. The 4.7 million polygons overlap ...
5
votes
2answers
233 views

Different models, different contours: are they comparable?

I will get contour lines of electromagnetic field strength around power lines. The contours will be calculated by different agencies using different models. We need to check whether the resulting ...
5
votes
3answers
2k views

Calculate neighborhood statistics for polygons?

I've been searching around for the answer to this (including here) and have yet to find it. I'm interested in finding out how to calculate a 'neighborhood sum' for vector, polygon data. I am aware ...
5
votes
1answer
652 views

QGis Zonal Statistics Plugin NoData included in Calculations

I have been trying to use the QGIS zonal statistics plugin. My raster has a nodata value of -99999 and all other values are positive. After computing the mean zonal statistics there are a number of ...
5
votes
0answers
251 views

Zonal Histogram Output Problems - No values associated with the habitat type [closed]

I have a outline of some islands (shapefile or raster) and GAP landcover data (raster). I am trying to use Zonal Histogram to create a file with a histogram of the habitat types in each island. Each ...
4
votes
2answers
118 views

how to get max and min from a raster using arcpy?

I have a land surface temperature raster file and I want the max and min of it. minLSTresult = arcpy.GetRasterProperties_management(raster_result, "MINIMUM") minLST = minLSTresult.getOutput(0) ...
4
votes
3answers
4k views

How to count occurrences of one field grouped by values of another?

Is there a way of calculating the number of unique text strings in a field in ArcGIS 10.1? I have a number of repeated strings in this field, but would like to calculate the number of unique strings ...
4
votes
1answer
860 views

How to use/interpret/visualise a distance matrix with unknown coordinates?

How would you go about using a distance matrix where points have no coordinates, i.e. what useful statistics can be made and how to visualise it in some useful way?
4
votes
2answers
3k views

GDAL does not ignore NoData value

I am trying to calcualate the statistics of a TIFF. The script should ignore the NoData value, but doesn't. What causes this? import gdal from gdalconst import * # register all of the drivers ...
4
votes
1answer
4k views

Detecting duplicate attribute values in table using ArcPy without Advanced/ArcInfo level license?

In ArcMap, the right-click Summarize option very quickly creates a frequency listing of the chosen field: Note that the count field shows the count of duplicate values. How can I access this ...
4
votes
1answer
102 views

Finding Median, Max and Min values from Raster Layers in QGIS

I currently have 10 years worth of January raster datasets (working on just one month at the moment) of cloud fraction cover from MODIS, and am trying to create new 3 separate rasters which will give ...
4
votes
1answer
33 views

raster statistics by line shape (vector)

I have a georeferenced area where I created 7 raster maps (classified with suitability values from 1 to 5) as I have 7 factors to check e.g. natural reserves, floods, slopes etc. From there I did a ...
4
votes
1answer
223 views

How to get counts from a table to produce a heatmap?

I am trying to create a heat map of doctors per zip code based on zip code. I have a table with the doctors and their zip codes, some of them repeating because there is more than one doctor per zip ...
4
votes
1answer
490 views

How to create Series of Rasters that displays Standard Deviation from Mean?

Cell statistics question for you. I have 100 rasters of raw rainfall data in which the pixels each represent rainfall for that particular pixel on the landscape for a single year during the 100 year ...
4
votes
1answer
84 views

Index express the similarity in shape between two data sets

I have two data sets. One is points in the blue curve. The other is points in the green curve. Now I want to find a property (P) or something else like index that has the following characteristics: ...
4
votes
0answers
390 views

How to analyse correlations between variables and points? [closed]

I have just lost the past 8 hours on this, and literally getting nowhere - hoping someone can help before I go mad! I am trying to determine the correlation between sinkholes and a number of ...
3
votes
2answers
1k views

min and max values are not correctly calculated for DEM

I'm working with DEM in QGIS and need to know the min and max values of my data. In the Properties window, under the Metadata tab, the statistics section shows such values. However, I usually find ...
3
votes
2answers
404 views

Performing statistical analysis of buffers?

I am doing a buffer analysis of incinerators and looking at the output areas within those buffers, is there a way of doing a statistical analysis of several buffers to see if there is a significant ...
3
votes
2answers
128 views

Retrieving LiDAR metrics from relative vertical layers of point cloud

I need to obtain the proportion of all returns within 5 equally spaced height bins between the cutoff (1 meter) and the maximum height value. I need to get this proportion of all returns for 1000 ...
3
votes
2answers
393 views

Methods for hot spot or cluster analysis for multiple measurements at the same geographic unit?

I would like to find geographic clusters of zip codes where each zip code has a measurement of a person's age (integer), sex (categorical/binary), and if they recovered from a certain medical ...
3
votes
2answers
2k views

How are kappa and overall accuracy related with respect to thematic raster data?

I recently calculated kappa (using confusionMatrix{caret} in R) between a thematic raster dataset at 1m spatial resolution and another at 30m spatial resolution. I was interested in quantifying the ...
3
votes
2answers
982 views

How to create a standard deviation map from three rasters in QGIS?

I have 3 normalised (0-100) raster maps. Is it possible to get a map which shows the standard deviation? I'd like to see the areas with smaller and higher std deviation. Thank you!