--- title: "PadRight" language: "en" type: "Symbol" summary: "PadRight[list, n] makes a list of length n by padding list with zeros on the right. PadRight[list, n, x] pads by repeating the element x. PadRight[list, n, {x1, x2, ...}] pads by cyclically repeating the elements xi. PadRight[list, n, padding, m] leaves a margin of m elements of padding on the left. PadRight[list, {n1, n2, ...}] makes a nested list with length ni at level i. PadRight[list] pads a ragged array list with zeros to make it full." keywords: - padding canonical_url: "https://reference.wolfram.com/language/ref/PadRight.html" source: "Wolfram Language Documentation" related_guides: - title: "Rearranging & Restructuring Lists" link: "https://reference.wolfram.com/language/guide/RearrangingAndRestructuringLists.en.md" - title: "Constructing Matrices" link: "https://reference.wolfram.com/language/guide/ConstructingMatrices.en.md" related_functions: - title: "PadLeft" link: "https://reference.wolfram.com/language/ref/PadLeft.en.md" - title: "ArrayPad" link: "https://reference.wolfram.com/language/ref/ArrayPad.en.md" - title: "Join" link: "https://reference.wolfram.com/language/ref/Join.en.md" - title: "Partition" link: "https://reference.wolfram.com/language/ref/Partition.en.md" - title: "ArrayReshape" link: "https://reference.wolfram.com/language/ref/ArrayReshape.en.md" - title: "CenterArray" link: "https://reference.wolfram.com/language/ref/CenterArray.en.md" - title: "ListCorrelate" link: "https://reference.wolfram.com/language/ref/ListCorrelate.en.md" - title: "Riffle" link: "https://reference.wolfram.com/language/ref/Riffle.en.md" - title: "RotateRight" link: "https://reference.wolfram.com/language/ref/RotateRight.en.md" - title: "StringPadRight" link: "https://reference.wolfram.com/language/ref/StringPadRight.en.md" related_tutorials: - title: "Rearranging Lists" link: "https://reference.wolfram.com/language/tutorial/Lists.en.md#1331" - title: "Nested Lists" link: "https://reference.wolfram.com/language/tutorial/ManipulatingLists.en.md#15721" - title: "Partitioning and Padding Lists" link: "https://reference.wolfram.com/language/tutorial/ManipulatingLists.en.md#14460" --- # PadRight PadRight[list, n] makes a list of length n by padding list with zeros on the right. PadRight[list, n, x] pads by repeating the element x. PadRight[list, n, {x1, x2, …}] pads by cyclically repeating the elements xi. PadRight[list, n, padding, m] leaves a margin of m elements of padding on the left. PadRight[list, {n1, n2, …}] makes a nested list with length ni at level i. PadRight[list] pads a ragged array list with zeros to make it full. ## Details * ``PadRight[list, n, …]`` always returns a list of length ``n``, except in some special cases where ``padding`` is ``{}``. * With padding ``{x1, x2, …, xs}``, cyclic repetitions of the ``xi`` are effectively laid down and then the list is superimposed on top of them, with the first element of the list lying on an occurrence of ``x1``. » * A margin of ``Round[(n - Length[list]) / 2]`` effectively centers ``list``. * ``PadRight[list, n, list]`` effectively treats ``list`` as cyclic. * ``PadRight[list, n, {xlist}]`` can be used to repeat an individual element that is itself a list. * ``PadRight[{}, n, {x1, x2, …}]`` repeats the sequence of ``xi`` as many times as fit in a list of length ``n``. * ``PadRight[list, {n1, n2, …}]`` creates a full array with dimensions ``{n1, n2, …}`` even if ``list`` is ragged. » * ``PadRight[list, Automatic, x]`` pads with ``x`` to make a full array. * Negative ``ni`` specify to pad on the left. * ``PadRight[list, {n1, n2}, {{x11, x12, …}, {x21, …}, …}]`` pads by repeating the block of ``xij``. * ``PadRight[list, {n1, n2, …}, list]`` effectively treats ``list`` as cyclic in every dimension. * ``PadRight[list, {n1, n2, …}, padding, {m1, m2, …}]`` uses margin ``mi`` at level ``i``. * The object ``list`` need not have head ``List``. * ``PadRight`` can be used on ``SparseArray`` objects. --- ## Examples (14) ### Basic Examples (6) Pad with ``0`` to make the list be of length 10: ```wl In[1]:= PadRight[{a, b, c}, 10] Out[1]= {a, b, c, 0, 0, 0, 0, 0, 0, 0} ``` --- Pad with ``x`` : ```wl In[1]:= PadRight[{a, b, c}, 10, x] Out[1]= {a, b, c, x, x, x, x, x, x, x} ``` --- Pad by repeating ``{x, y, z}`` : ```wl In[1]:= PadRight[{a, b, c}, 10, {x, y, z}] Out[1]= {a, b, c, x, y, z, x, y, z, x} ``` --- Leave margin ``2`` on the left: ```wl In[1]:= PadRight[{a, b, c}, 10, x, 2] Out[1]= {x, x, a, b, c, x, x, x, x, x} ``` --- Pad to make a 3×4 array: ```wl In[1]:= PadRight[{{a, b}, {c}}, {3, 4}]//TableForm Out[1]//TableForm= | | | | | | :- | :- | :- | :- | | a | b | 0 | 0 | | c | 0 | 0 | 0 | | 0 | 0 | 0 | 0 | ``` --- Pad to make a full array: ```wl In[1]:= PadRight[{{a, b, c}, {d, e}, {f}}]//TableForm Out[1]//TableForm= | | | | | :- | :- | :- | | a | b | c | | d | e | 0 | | f | 0 | 0 | ``` ### Scope (3) Negative length specifications pad on the left: ```wl In[1]:= PadRight[{a, b, c}, -10] Out[1]= {0, 0, 0, 0, 0, 0, 0, a, b, c} ``` --- Lay down repetitions of the padding, then superimpose the original array: ```wl In[1]:= PadRight[{{aa, bb}, {cc}}, {4, 4}, {{x, y}, {z}}]//TableForm Out[1]//TableForm= | | | | | | :- | :- | :- | :- | | aa | bb | x | y | | cc | z | z | z | | x | y | x | y | | z | z | z | z | ``` --- Use different margins for rows and columns: ```wl In[1]:= PadRight[{{aa, bb}, {cc}}, {5, 5}, {{x, y}, {z}}, {1, 2}]//TableForm Out[1]//TableForm= | | | | | | | :- | :- | :- | :- | :- | | z | z | z | z | z | | x | y | aa | bb | x | | z | z | cc | z | z | | x | y | x | y | x | | z | z | z | z | z | ``` ### Generalizations & Extensions (1) Use a head other than ``List`` : ```wl In[1]:= PadRight[f[a, b, c], 8, x] Out[1]= f[a, b, c, x, x, x, x, x] ``` ### Applications (2) Put a ``1`` at the center of a list of ``0``s: ```wl In[1]:= PadRight[{1}, 19, 0, 9] Out[1]= {0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0} ``` --- Lay out an array of tiles: ```wl In[1]:= ArrayPlot[PadRight[{{}}, {15, 15}, {{1, 0, 1}, {0, 1, 1}, {1, 0, 0}}], Mesh -> True] Out[1]= [image] ``` ### Properties & Relations (1) ``PadLeft[list, n]`` and ``PadRight[list, n]`` pad to make a list of length ``n`` : ```wl In[1]:= PadLeft[{1, 2, 3}, 5] Out[1]= {0, 0, 1, 2, 3} In[2]:= PadRight[{1, 2, 3}, 5] Out[2]= {1, 2, 3, 0, 0} ``` ``ArrayPad[list, n]`` pads with ``n`` additional elements on each side: ```wl In[3]:= ArrayPad[{1, 2, 3}, 5] Out[3]= {0, 0, 0, 0, 0, 1, 2, 3, 0, 0, 0, 0, 0} ``` ### Possible Issues (1) Pad with an element that is itself a list: ```wl In[1]:= PadRight[{a, b, c}, 7, {{u, v}}] Out[1]= {a, b, c, {u, v}, {u, v}, {u, v}, {u, v}} In[2]:= PadRight[{a, b, c}, 7, {u, v}] Out[2]= {a, b, c, v, u, v, u} ``` ## See Also * [`PadLeft`](https://reference.wolfram.com/language/ref/PadLeft.en.md) * [`ArrayPad`](https://reference.wolfram.com/language/ref/ArrayPad.en.md) * [`Join`](https://reference.wolfram.com/language/ref/Join.en.md) * [`Partition`](https://reference.wolfram.com/language/ref/Partition.en.md) * [`ArrayReshape`](https://reference.wolfram.com/language/ref/ArrayReshape.en.md) * [`CenterArray`](https://reference.wolfram.com/language/ref/CenterArray.en.md) * [`ListCorrelate`](https://reference.wolfram.com/language/ref/ListCorrelate.en.md) * [`Riffle`](https://reference.wolfram.com/language/ref/Riffle.en.md) * [`RotateRight`](https://reference.wolfram.com/language/ref/RotateRight.en.md) * [`StringPadRight`](https://reference.wolfram.com/language/ref/StringPadRight.en.md) ## Tech Notes * [Rearranging Lists](https://reference.wolfram.com/language/tutorial/Lists.en.md#1331) * [Nested Lists](https://reference.wolfram.com/language/tutorial/ManipulatingLists.en.md#15721) * [Partitioning and Padding Lists](https://reference.wolfram.com/language/tutorial/ManipulatingLists.en.md#14460) ## Related Guides * [Rearranging & Restructuring Lists](https://reference.wolfram.com/language/guide/RearrangingAndRestructuringLists.en.md) * [Constructing Matrices](https://reference.wolfram.com/language/guide/ConstructingMatrices.en.md) ## History * Introduced in 1999 (4.0) \| Updated in 2003 (5.0) ▪ [2007 (6.0)](https://reference.wolfram.com/language/guide/SummaryOfNewFeaturesIn60.en.md)