# NDArrayExpression¶

class hail.expr.NDArrayExpression[source]

Expression of type tndarray.

>>> nd = hl.nd.array([[1, 2], [3, 4]])


Attributes

 T Reverse the dimensions of this ndarray. dtype The data type of the expression. ndim The number of dimensions of this ndarray. shape The shape of this ndarray.

Methods

 map Applies an element-wise operation on an NDArray. map2 Applies an element-wise binary operation on two NDArrays. reshape Reshape this ndarray to a new shape. transpose Permute the dimensions of this ndarray according to the ordering of axes.
property T

Reverse the dimensions of this ndarray. For an n-dimensional array a, a[i_0, …, i_n-1, i_n] = a.T[i_n, i_n-1, …, i_0]. Same as self.transpose().

See also transpose().

Returns
__eq__(other)

Returns True if the two expressions are equal.

Examples

>>> x = hl.literal(5)
>>> y = hl.literal(5)
>>> z = hl.literal(1)

>>> hl.eval(x == y)
True

>>> hl.eval(x == z)
False


Notes

This method will fail with an error if the two expressions are not of comparable types.

Parameters

other (Expression) – Expression for equality comparison.

Returns

BooleanExpressionTrue if the two expressions are equal.

__ge__(other)

Return self>=value.

__gt__(other)

Return self>value.

__le__(other)

Return self<=value.

__lt__(other)

Return self<value.

__ne__(other)

Returns True if the two expressions are not equal.

Examples

>>> x = hl.literal(5)
>>> y = hl.literal(5)
>>> z = hl.literal(1)

>>> hl.eval(x != y)
False

>>> hl.eval(x != z)
True


Notes

This method will fail with an error if the two expressions are not of comparable types.

Parameters

other (Expression) – Expression for inequality comparison.

Returns

BooleanExpressionTrue if the two expressions are not equal.

collect(_localize=True)

Collect all records of an expression into a local list.

Examples

Collect all the values from C1:

>>> table1.C1.collect()
[2, 2, 10, 11]


Warning

Extremely experimental.

Warning

The list of records may be very large.

Returns

list

describe(handler=<built-in function print>)

Print information about type, index, and dependencies.

property dtype

The data type of the expression.

Returns

HailType

export(path, delimiter='\t', missing='NA', header=True)

Export a field to a text file.

Examples

>>> small_mt.GT.export('output/gt.tsv')
>>> with open('output/gt.tsv', 'r') as f:
...     for line in f:
...         print(line, end='')
locus   alleles 0       1       2       3
1:1     ["A","C"]       1/1     1/1     0/1     0/1
1:2     ["A","C"]       1/1     1/1     0/0     1/1
1:3     ["A","C"]       0/0     0/0     0/1     0/0
1:4     ["A","C"]       1/1     0/1     1/1     0/1

>>> small_mt.GT.export('output/gt-no-header.tsv', header=False)
>>> with open('output/gt-no-header.tsv', 'r') as f:
...     for line in f:
...         print(line, end='')
1:1     ["A","C"]       1/1     1/1     0/1     0/1
1:2     ["A","C"]       1/1     1/1     0/0     1/1
1:3     ["A","C"]       0/0     0/0     0/1     0/0
1:4     ["A","C"]       1/1     0/1     1/1     0/1

>>> small_mt.pop.export('output/pops.tsv')
>>> with open('output/pops.tsv', 'r') as f:
...     for line in f:
...         print(line, end='')
sample_idx      pop
0       0
1       0
2       2
3       0

>>> small_mt.ancestral_af.export('output/ancestral_af.tsv')
>>> with open('output/ancestral_af.tsv', 'r') as f:
...     for line in f:
...         print(line, end='')
locus   alleles ancestral_af
1:1     ["A","C"]       5.6562e-01
1:2     ["A","C"]       3.6521e-01
1:3     ["A","C"]       2.6421e-01
1:4     ["A","C"]       6.5715e-01

>>> small_mt.bn.export('output/bn.tsv')
>>> with open('output/bn.tsv', 'r') as f:
...     for line in f:
...         print(line, end='')
bn
{"n_populations":3,"n_samples":4,"n_variants":4,"n_partitions":8,"pop_dist":[1,1,1],"fst":[0.1,0.1,0.1],"mixture":false}


Notes

For entry-indexed expressions, if there is one column key field, the result of calling str() on that field is used as the column header. Otherwise, each compound column key is converted to JSON and used as a column header. For example:

>>> small_mt = small_mt.key_cols_by(s=small_mt.sample_idx, family='fam1')
>>> with open('output/gt-no-header.tsv', 'r') as f:
...     for line in f:
...         print(line, end='')
locus   alleles {"s":0,"family":"fam1"} {"s":1,"family":"fam1"} {"s":2,"family":"fam1"} {"s":3,"family":"fam1"}
1:1     ["A","C"]       1/1     1/1     0/1     0/1
1:2     ["A","C"]       1/1     1/1     0/0     1/1
1:3     ["A","C"]       0/0     0/0     0/1     0/0
1:4     ["A","C"]       1/1     0/1     1/1     0/1

Parameters
map(f)[source]

Applies an element-wise operation on an NDArray.

Parameters

f (function ( (arg) -> Expression)) – Function to transform each element of the NDArray.

Returns

NDArrayExpression. – NDArray where each element has been transformed according to f.

map2(other, f)[source]

Applies an element-wise binary operation on two NDArrays.

Parameters
• other (class:.NDArrayExpression, ArrayExpression, numpy NDarray,) – or nested python list/tuples. Both NDArrays must be the same shape or broadcastable into common shape.

• f (function ((arg1, arg2)-> Expression)) – Function to be applied to each element of both NDArrays.

Returns

NDArrayExpression. – Element-wise result of applying f to each index in NDArrays.

property ndim

The number of dimensions of this ndarray.

Examples

>>> nd.ndim
2

Returns

int

reshape(*shape)[source]

Reshape this ndarray to a new shape.

Parameters

shape (Expression of type tint64 or) – :obj: tuple of Expression of type tint64

Examples

>>> v = hl.nd.array([1, 2, 3, 4])
>>> m = v.reshape((2, 2))

Returns
property shape

The shape of this ndarray.

Examples

>>> hl.eval(nd.shape)
(2, 2)

Returns

TupleExpression

show(n=None, width=None, truncate=None, types=True, handler=None, n_rows=None, n_cols=None)

Print the first few records of the expression to the console.

If the expression refers to a value on a keyed axis of a table or matrix table, then the accompanying keys will be shown along with the records.

Examples

>>> table1.SEX.show()
+-------+-----+
|    ID | SEX |
+-------+-----+
| int32 | str |
+-------+-----+
|     1 | "M" |
|     2 | "M" |
|     3 | "F" |
|     4 | "F" |
+-------+-----+

>>> hl.literal(123).show()
+--------+
| <expr> |
+--------+
|  int32 |
+--------+
|    123 |
+--------+


Notes

The output can be passed piped to another output source using the handler argument:

>>> ht.foo.show(handler=lambda x: logging.info(x))

Parameters
• n (int) – Maximum number of rows to show.

• width (int) – Horizontal width at which to break columns.

• truncate (int, optional) – Truncate each field to the given number of characters. If None, truncate fields to the given width.

• types (bool) – Print an extra header line with the type of each field.

summarize(handler=None)

Compute and print summary information about the expression.

Danger

This functionality is experimental. It may not be tested as well as other parts of Hail and the interface is subject to change.

take(n, _localize=True)

Collect the first n records of an expression.

Examples

Take the first three rows:

>>> table1.X.take(3)
[5, 6, 7]


Warning

Extremely experimental.

Parameters

n (int) – Number of records to take.

Returns

list

transpose(axes=None)[source]

Permute the dimensions of this ndarray according to the ordering of axes. Axis j in the ith index of axes maps the jth dimension of the ndarray to the ith dimension of the output ndarray.

Parameters

axes (tuple of int, optional) – The new ordering of the ndarray’s dimensions.

Notes

Does nothing on ndarrays of dimensionality 0 or 1.

Returns