Also, create another array filled with no-data values that is the same shape and data type as the initial array. Then use arange to create a 7×7 array with values that range from 1 to 48. To implement some simple examples, let’s create the array shown above. For simplicity, we’ll exclude edge elements in this article.ģ by 3 sliding window Create a NumPy Array Because of this many analyses exclude edge elements. It’s important to note that special accommodations must be made for edge elements because they don’t have 9 neighbors. But at its core, moving window analysis can be summed up as simply as the mean of neighbor elements. Larger window sizes, or non-square windows can be used. Finite difference approaches can be used for temporal and spatial data. Of course, things can get much more complicated. This is done for each element in the array. Instead of the mean, you could calculate the minimum value (0), the maximum value (16), or a number of other metrics. For example, in the image below, we could calculate the mean of the 9 elements in the grey window (spoiler alert, the mean is also 8) and assign it to the target element, which is outlined in red. This is the array location the sliding window will calculate a new metric for. The array element outlined in red is the target element. The example below shows a 3×3 (3 by 3) sliding window.
#PYTHON CREATE WINDOWS GRID FROM ARRAYS HOW TO#
Learning how to implement moving windows will take your data analysis and wrangling skills up to a new level. They’re also very easy to implement in Python.
Sliding window operations are extremely prevalent and extremely useful.
Anytime you do analysis on data formatted as a two-dimensional array there’s a good chance a sliding window will be involved. Do you do terrain analysis in GIS? Most topographic raster metrics (slope, aspect, hillshade, etc.) are based on sliding windows. Have you done any photo editing? Many editing algorithms are based on moving windows. There’s a good chance you’ve done something today that used a sliding window (also known as a moving window) and you didn’t even know it.
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