changem

Replace values in array

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    Syntax

    B = changem(A,new)
    B = changem(A,new,old)

    Description

    B = changem(A,new) replaces all occurrences of 0 in array A with the specified scalar new. This function is useful for replacing values in classification grids.

    B = changem(A,new,old) replaces all occurrences of old with new.

    example

    Examples

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    Open Live Script

    Read a land cover classification of Oahu, Hawaii [1] as a matrix, a map cells reference object, and a colormap. The elements of the matrix index into the colormap.

    [A,R,cmap] = readgeoraster("oahu_landcover.img");

    Deciduous forest, evergreen forest, and mixed forest are indicated by the values 9, 10, and 11 in the matrix, respectively. Create a matrix that uses the same color for all forests by replacing occurrences of 9 and 10 with 11.

    new = [11 11];
old = [9 10];
B = changem(A,new,old);

    Display the original land cover classification on a map. Set up the map using the projected coordinate reference system (CRS) that is stored in the reference object. Prepare to display the data with the geoimage function by converting the indexed image to an RGB image. 

    figure
newmap(R.ProjectedCRS)
A_RGB = ind2rgb(A,cmap);
geoimage(A_RGB,R)
title("Land Cover Classification with Three Forest Types")

    Figure contains an axes object with type mapaxes. The mapaxes object contains an object of type rasterimage.

    Display the updated land cover classification on a similar map. 

    figure
newmap(R.ProjectedCRS)
B_RGB = ind2rgb(B,cmap);
geoimage(B_RGB,R)
title("Land Cover Classification with One Forest Type")

    Figure contains an axes object with type mapaxes. The mapaxes object contains an object of type rasterimage.

    [1] The data used in this example is courtesy of the National Oceanic and Atmospheric Administration (NOAA).

    Input Arguments

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    Input array.

    New value, specified as a scalar or vector. When new and old are vectors, the function replaces occurrences of old(k) with new(k).

    The size of new must match the size of old.

    Value to replace, specified as a scalar or vector. When new and old are vectors, the function replaces occurrences of old(k) with new(k).

    The size of new must match the size of old.

    Version History

    Introduced before R2006a

    See Also

    Functions