# Documentation

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# mapinterp

Map raster interpolation

## Syntax

``Vq = mapinterp(V,R,xq,yq)``
``Vq = mapinterp(___,method)``

## Description

example

````Vq = mapinterp(V,R,xq,yq)` interpolates the spatially referenced raster `V`, using bilinear interpolation. The function returns a value in `Vq` for each of the query points in arrays `xq` and `yq`. `R` is a map raster reference object that specifies the location and extent of data in `V`.```
````Vq = mapinterp(___,method)` specifies alternate interpolation methods.```

## Examples

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Load a spatially referenced raster grid and a map raster reference object. This example uses projected elevation data for Mt. Washington.

`[Z, R] = arcgridread('MtWashington-ft.grd','planar');`

Display the data using mapshow.

```figure mapshow(Z,R,'DisplayType','texturemap') colorbar```

Define the points you want to interpolate.

```x = [312829 317447 316083 311150]; y = [4913618 4912253 4904329 4904172];```

Interpolate the values at the defined points.

`Vinterpolated = mapinterp(Z,R,x,y)`
```Vinterpolated = 1.0e+03 * 1.5240 3.6780 6.2363 2.3646 ```

## Input Arguments

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Spatially referenced raster grid, specified as numeric or logical array.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `logical`

Map raster, specified as a `MapCellsReference` or `MapPostingsReference` object.

To convert a referencing matrix to a map raster reference object, use `refmatToMapRasterReference`.

Query point coordinates in x dimension, specified as a numeric array.

Data Types: `single` | `double`

Query point coordinates in y dimension, specified as a numeric array.

Data Types: `single` | `double`

Interpolation methods, specified as one of these character vectors or strings.

MethodDescription
`'nearest'`Nearest neighbor interpolation
`'linear'`Bilinear interpolation
`'cubic'`Bicubic interpolation
`'spline'`Spline interpolation

Data Types: `char` | `string`

## Output Arguments

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Interpolated values, returned as a numeric array.