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# interp1q

Quick 1-D linear interpolation

 Note:   interp1q is not recommended. Use interp1 instead.

## Syntax

yi = interp1q(x,Y,xi)

## Description

yi = interp1q(x,Y,xi) returns the value of the 1-D function Y at the points of column vector xi using linear interpolation. The vector x specifies the coordinates of the underlying interval. The length of output yi is equal to the length of xi.

interp1q is quicker than interp1 on non-uniformly spaced data because it does no input checking.

For interp1q to work properly,

• x must be a monotonically increasing column vector.

• Y must be a column vector or matrix with length(x) rows.

• xi must be a column vector

interp1q returns NaN for any values of xi that lie outside the coordinates in x. If Y is a matrix, then the interpolation is performed for each column of Y, in which case yi is length(xi)-by-size(Y,2).

## Examples

expand all

### Linear Interpolation Using interp1q

Generate a coarse sine curve and interpolate over a finer abscissa.

```x = (0:10)';
y = sin(x);
xi = (0:.25:10)';
yi = interp1q(x,y,xi);
plot(x,y,'o',xi,yi)
```

## See Also

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