interp1

interp1#

Piecewise interpolation with various methods (linear, nearest, next, previous, spline).

Added in version 0.9.1.

template<typename OpX, typename OpV, typename OpXQ>
auto matx::interp1(const OpX &x, const OpV &v, const OpXQ &xq, InterpMethod method = InterpMethod::LINEAR)#

1D interpolation of samples at query points.

Interpolation is performed along the last dimension. All other dimensions must be of compatible size.

Template Parameters:

  • OpX – Type of sample points

  • OpV – Type of sample values

  • OpXQ – Type of query points

Parameters:

  • x – Sample points. Last dimension must be sorted in ascending order.

  • v – Sample values. Must have compatible dimensions with x.

  • xq – Query points where to interpolate. All dimensions except the last must be of compatible size with x and v (e.g. x and v can be vectors, and xq can be a matrix).

  • method – Interpolation method (LINEAR, NEAREST, NEXT, PREV, SPLINE)

Returns:

Operator that interpolates values at query points, with the same dimensions as xq.

template<typename OpX, typename OpV, typename OpXQ>
auto matx::interp1(const OpX &x, const OpV &v, const OpXQ &xq, const int (&axis)[1], InterpMethod method = InterpMethod::LINEAR)#

1D interpolation of samples at query points.

Interpolation is performed along the specified dimension. All other dimensions must be of compatible size.

Template Parameters:

  • OpX – Type of sample points

  • OpV – Type of sample values

  • OpXQ – Type of query points

Parameters:

  • x – Sample points. Last dimension must be sorted in ascending order.

  • v – Sample values. Must have compatible dimensions with x.

  • xq – Query points where to interpolate. All dimensions except the specified dimension must be of compatible size with x and v (e.g. x and v can be vectors, and xq can be a matrix).

  • axis – Dimension (of xq) along which to interpolate.

  • method – Interpolation method (LINEAR, NEAREST, NEXT, PREV, SPLINE)

Returns:

Operator that interpolates values at query points, with the same dimensions as xq.

Interpolation Methods#

enum class matx::InterpMethod#

Interpolation method enumeration.

Specifies the algorithm to use when performing interpolation between sample points.

Values:

enumerator LINEAR#

Linear interpolation between adjacent points.

enumerator NEAREST#

Uses the value at the nearest sample point.

enumerator NEXT#

Uses the value at the next sample point.

enumerator PREV#

Uses the value at the previous sample point.

enumerator SPLINE#

Cubic spline interpolation, using not-a-knot boundary conditions.

Examples#

Linear Interpolation (default):

auto x = make_tensor<TestType>({5});
x.SetVals({static_cast<TestType>(0.0), static_cast<TestType>(1.0), static_cast<TestType>(3.0), static_cast<TestType>(3.5), static_cast<TestType>(4.0)});

auto v = make_tensor<TestType>(x.Shape());
v.SetVals({static_cast<TestType>(0.0), static_cast<TestType>(2.0), static_cast<TestType>(1.0), static_cast<TestType>(3.0), static_cast<TestType>(4.0)});

auto xq = make_tensor<TestType>({6});
xq.SetVals({static_cast<TestType>(-1.0), static_cast<TestType>(0.0), static_cast<TestType>(0.25), static_cast<TestType>(1.0), static_cast<TestType>(1.5), static_cast<TestType>(5.0)});

auto vq_linear = make_tensor<TestType>({xq.Size(0)});
vq_linear.SetVals({static_cast<TestType>(0.0), static_cast<TestType>(0.0), static_cast<TestType>(0.5), static_cast<TestType>(2.0), static_cast<TestType>(1.75), static_cast<TestType>(4.0)});

auto vq_nearest = make_tensor<TestType>({xq.Size(0)});
vq_nearest.SetVals({static_cast<TestType>(0.0), static_cast<TestType>(0.0), static_cast<TestType>(0.0), static_cast<TestType>(2.0), static_cast<TestType>(2.0), static_cast<TestType>(4.0)});

auto vq_next = make_tensor<TestType>({xq.Size(0)});
vq_next.SetVals({static_cast<TestType>(0.0), static_cast<TestType>(0.0), static_cast<TestType>(2.0), static_cast<TestType>(2.0), static_cast<TestType>(1.0), static_cast<TestType>(4.0)});

auto vq_prev = make_tensor<TestType>({xq.Size(0)});
vq_prev.SetVals({static_cast<TestType>(0.0), static_cast<TestType>(0.0), static_cast<TestType>(0.0), static_cast<TestType>(2.0), static_cast<TestType>(2.0), static_cast<TestType>(4.0)});

auto vq_spline = make_tensor<TestType>({xq.Size(0)});
vq_spline.SetVals({static_cast<TestType>(-10.7391), static_cast<TestType>(0.0), static_cast<TestType>(1.1121), static_cast<TestType>(2.0), static_cast<TestType>(1.3804), static_cast<TestType>(-8.1739)});



auto out_linear = make_tensor<TestType>({xq.Size(0)});
(out_linear = interp1(x, v, xq, InterpMethod::LINEAR)).run(exec);

Nearest Neighbor Interpolation:

auto out_nearest = make_tensor<TestType>({xq.Size(0)});
(out_nearest = interp1(x, v, xq, InterpMethod::NEAREST)).run(exec);
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