xbuilder¶
Defined in xtensor/xbuilder.hpp
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template<class T, class S>
inline auto xt::ones(S shape) noexcept¶ Returns an xexpression containing ones of the specified shape.
- Template Parameters
shape – the shape of the returned expression.
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template<class T, class S>
inline auto xt::zeros(S shape) noexcept¶ Returns an xexpression containing zeros of the specified shape.
- Template Parameters
shape – the shape of the returned expression.
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template<class T, layout_type L = ::xt::layout_type::row_major, class S>
inline xarray<T, L> xt::empty(const S &shape)¶ Create a xcontainer (xarray, xtensor or xtensor_fixed) with uninitialized values of with value_type T and shape.
Selects the best container match automatically from the supplied shape.
std::vector
→xarray<T>
std::array
orinitializer_list
→xtensor<T, N>
xshape<N...>
→xtensor_fixed<T, xshape<N...>>
- Parameters
shape – shape of the new xcontainer
Warning
doxygenfunction: Unable to resolve function “xt::full_like” with arguments (const xexpression<E>&) in doxygen xml output for project “xtensor” from directory: ../xml. Potential matches:
- template<class E> auto full_like(const xexpression<E> &e, typename E::value_type fill_value)
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template<class E>
inline auto xt::empty_like(const xexpression<E> &e)¶ Create a xcontainer (xarray, xtensor or xtensor_fixed) with uninitialized values of the same shape, value type and layout as the input xexpression e.
- Parameters
e – the xexpression from which to extract shape, value type and layout.
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template<class E>
inline auto xt::zeros_like(const xexpression<E> &e)¶ Create a xcontainer (xarray, xtensor or xtensor_fixed), filled with zeros and of the same shape, value type and layout as the input xexpression e.
Note: contrary to zeros(shape), this function returns a non-lazy, allocated container! Use `
xt::zeros<double>(e.shape());
for a lazy version.- Parameters
e – the xexpression from which to extract shape, value type and layout.
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template<class E>
inline auto xt::ones_like(const xexpression<E> &e)¶ Create a xcontainer (xarray, xtensor or xtensor_fixed), filled with ones and of the same shape, value type and layout as the input xexpression e.
Note: contrary to ones(shape), this function returns a non-lazy, evaluated container! Use
xt::ones<double>(e.shape());
for a lazy version.- Parameters
e – the xexpression from which to extract shape, value type and layout.
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template<class T = bool>
inline auto xt::eye(const std::vector<std::size_t> &shape, int k = 0)¶ Generates an array with ones on the diagonal.
- Parameters
shape – shape of the resulting expression
k – index of the diagonal. 0 (default) refers to the main diagonal, a positive value refers to an upper diagonal, and a negative value to a lower diagonal.
- Template Parameters
T – value_type of xexpression
- Returns
xgenerator that generates the values on access
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template<class T = bool>
inline auto xt::eye(std::size_t n, int k = 0)¶ Generates a (n x n) array with ones on the diagonal.
- Parameters
n – length of the diagonal.
k – index of the diagonal. 0 (default) refers to the main diagonal, a positive value refers to an upper diagonal, and a negative value to a lower diagonal.
- Template Parameters
T – value_type of xexpression
- Returns
xgenerator that generates the values on access
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template<class T, class S = T>
inline auto xt::arange(T start, T stop, S step = 1) noexcept¶ Generates numbers evenly spaced within given half-open interval [start, stop).
- Parameters
start – start of the interval
stop – stop of the interval
step – stepsize
- Template Parameters
T – value_type of xexpression
- Returns
xgenerator that generates the values on access
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template<class T>
inline auto xt::arange(T stop) noexcept¶ Generate numbers evenly spaced within given half-open interval [0, stop) with a step size of 1.
- Parameters
stop – stop of the interval
- Template Parameters
T – value_type of xexpression
- Returns
xgenerator that generates the values on access
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template<class T>
inline auto xt::linspace(T start, T stop, std::size_t num_samples = 50, bool endpoint = true) noexcept¶ Generates num_samples evenly spaced numbers over given interval.
- Parameters
start – start of interval
stop – stop of interval
num_samples – number of samples (defaults to 50)
endpoint – if true, include endpoint (defaults to true)
- Template Parameters
T – value_type of xexpression
- Returns
xgenerator that generates the values on access
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template<class T>
inline auto xt::logspace(T start, T stop, std::size_t num_samples, T base = 10, bool endpoint = true) noexcept¶ Generates num_samples numbers evenly spaced on a log scale over given interval.
- Parameters
start – start of interval (pow(base, start) is the first value).
stop – stop of interval (pow(base, stop) is the final value, except if endpoint = false)
num_samples – number of samples (defaults to 50)
base – the base of the log space.
endpoint – if true, include endpoint (defaults to true)
- Template Parameters
T – value_type of xexpression
- Returns
xgenerator that generates the values on access
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template<class ...CT>
inline auto xt::concatenate(std::tuple<CT...> &&t, std::size_t axis = 0)¶ Concatenates xexpressions along axis.
xt::xarray<double> a = {{1, 2, 3}}; xt::xarray<double> b = {{2, 3, 4}}; xt::xarray<double> c = xt::concatenate(xt::xtuple(a, b)); // => {{1, 2, 3}, // {2, 3, 4}} xt::xarray<double> d = xt::concatenate(xt::xtuple(a, b), 1); // => {{1, 2, 3, 2, 3, 4}}
- Parameters
t – xtuple of xexpressions to concatenate
axis – axis along which elements are concatenated
- Returns
xgenerator evaluating to concatenated elements
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template<class ...CT>
inline auto xt::stack(std::tuple<CT...> &&t, std::size_t axis = 0)¶ Stack xexpressions along axis.
Stacking always creates a new dimension along which elements are stacked.
xt::xarray<double> a = {1, 2, 3}; xt::xarray<double> b = {5, 6, 7}; xt::xarray<double> s = xt::stack(xt::xtuple(a, b)); // => {{1, 2, 3}, // {5, 6, 7}} xt::xarray<double> t = xt::stack(xt::xtuple(a, b), 1); // => {{1, 5}, // {2, 6}, // {3, 7}}
- Parameters
t – xtuple of xexpressions to concatenate
axis – axis along which elements are stacked
- Returns
xgenerator evaluating to stacked elements
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template<class ...CT>
inline auto xt::hstack(std::tuple<CT...> &&t)¶ Stack xexpressions in sequence horizontally (column wise).
This is equivalent to concatenation along the second axis, except for 1-D xexpressions where it concatenate along the firts axis.
- Parameters
t – xtuple of xexpressions to stack
- Returns
xgenerator evaluating to stacked elements
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template<class ...CT>
inline auto xt::vstack(std::tuple<CT...> &&t)¶ Stack xexpressions in sequence vertically (row wise).
This is equivalent to concatenation along the first axis after 1-D arrays of shape (N) have been reshape to (1, N).
- Parameters
t – xtuple of xexpressions to stack
- Returns
xgenerator evaluating to stacked elements
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template<class ...E>
inline auto xt::meshgrid(E&&... e) noexcept¶ Return coordinate tensors from coordinate vectors.
Make N-D coordinate tensor expressions for vectorized evaluations of N-D scalar/vector fields over N-D grids, given one-dimensional coordinate arrays x1, x2,…, xn.
- Parameters
e – xexpressions to concatenate
- Returns
tuple of xgenerator expressions.
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template<class E>
inline auto xt::diag(E &&arr, int k = 0)¶ xexpression with values of arr on the diagonal, zeroes otherwise
xt::xarray<double> a = {1, 5, 9}; auto b = xt::diag(a); // => {{1, 0, 0}, // {0, 5, 0}, // {0, 0, 9}}
- Parameters
arr – the 1D input array of length n
k – the offset of the considered diagonal
- Returns
xexpression function with shape n x n and arr on the diagonal
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template<class E>
inline auto xt::diagonal(E &&arr, int offset = 0, std::size_t axis_1 = 0, std::size_t axis_2 = 1)¶ Returns the elements on the diagonal of arr If arr has more than two dimensions, then the axes specified by axis_1 and axis_2 are used to determine the 2-D sub-array whose diagonal is returned.
The shape of the resulting array can be determined by removing axis1 and axis2 and appending an index to the right equal to the size of the resulting diagonals.
xt::xarray<double> a = {{1, 2, 3}, {4, 5, 6} {7, 8, 9}}; auto b = xt::diagonal(a); // => {1, 5, 9}
- Parameters
arr – the input array
offset – offset of the diagonal from the main diagonal. Can be positive or negative.
axis_1 – Axis to be used as the first axis of the 2-D sub-arrays from which the diagonals should be taken.
axis_2 – Axis to be used as the second axis of the 2-D sub-arrays from which the diagonals should be taken.
- Returns
xexpression with values of the diagonal
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template<class E>
inline auto xt::tril(E &&arr, int k = 0)¶ Extract lower triangular matrix from xexpression.
The parameter k selects the offset of the diagonal.
- Parameters
arr – the input array
k – the diagonal above which to zero elements. 0 (default) selects the main diagonal, k < 0 is below the main diagonal, k > 0 above.
- Returns
xexpression containing lower triangle from arr, 0 otherwise
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template<class E>
inline auto xt::triu(E &&arr, int k = 0)¶ Extract upper triangular matrix from xexpression.
The parameter k selects the offset of the diagonal.
- Parameters
arr – the input array
k – the diagonal below which to zero elements. 0 (default) selects the main diagonal, k < 0 is below the main diagonal, k > 0 above.
- Returns
xexpression containing lower triangle from arr, 0 otherwise