Operation Flashpoint scripting language, 182 bytes

f={t=_this;c=count(t select 0);e=[0];i=0;while{i<c*2}do{e=e+[0];i=i+1};m=[e];i=0;while{i<count t}do{r=+e;j=0;while{j<c}do{r set[j*2+1,(t select i)select j];j=j+1};m=m+[r,e];i=i+1};m} 

Ungolfed:

f= { // _this is the input matrix. Let's give it a shorter name to save bytes. t = _this; c = count (t select 0); // Create a row of c*2+1 zeros, where c is the number of columns in the // original matrix. e = [0]; i = 0; while {i < c*2} do { e = e + [0]; i = i + 1 }; m = [e]; // The exploded matrix, which starts with a row of zeros. i = 0; while {i < count t} do { // Make a copy of the row of zeros, and add to its every other column // the values from the corresponding row of the original matrix. r = +e; j = 0; while {j < c} do { r set [j*2+1, (t select i) select j]; j = j + 1 }; // Add the new row and a row of zeroes to the exploded matrix. m = m + [r, e]; i = i + 1 }; // The last expression is returned. m } 

Call with:

hint format["%1\n\n%2\n\n%3\n\n%4", [[1]] call f, [[1, 4], [5, 2]] call f, [[1, 4, 7]] call f, [[6],[4],[2]] call f]; 

Output:

In the spirit of the challenge:

Jelly,  12  11 bytes

-1 byte thanks to Erik the Outgolfer (no need to use swapped arguments for a join)

j00,0jµ€Z$⁺ 

Try it online! Or see a test suite.

A monadic link accepting and returning lists of lists.

How?

j00,0jµ€Z$⁺ - Link: list of lists, m ⁺ - perform the link to the left twice in succession: $ - last two links as a monad µ€ - perform the chain to the left for €ach row in the current matrix: j0 - join with zeros [a,b,...,z] -> [a,0,b,0,...,0,z] 0,0 - zero paired with zero = [0,0] j - join [a,0,b,0,...,0,z] -> [0,a,0,b,0,...,0,z,0] Z - and then transpose the resulting matrix 

Haskell, 38 bytes

a%l=a:(=<<)(:[a])l f l=(0%)<$>(0<$l)%l 

Try it online!

MATL, 12 bytes

FTXdX*0JQt&( 

Input is a matrix with ; as row separator.

Try it online!

Explanation

FT % Push [0 1] Xd % Matrix with that diagonal: gives [0 0; 0 1] X* % Implicit input. Kronecker product 0 % Push 0 JQt % Push 1+j (interpreted as "end+1" index) twice &( % Write a 0 at (end+1, end+1), extending the matrix. Implicit display 

Japt, 18 bytes

Ov"y ®î íZ c p0Ã"² 

Test it online! (Uses the -Q flag so the output is easier to understand.)

Similar to the Jelly answer, but a whole lot longer...

Explanation

The outer part of the code is just a workaround to simulate Jelly's ⁺:

 " "² Repeat this string twice. Ov Evaluate it as Japt. 

The code itself is:

y ® î íZ c p0Ã y mZ{Zî íZ c p0} Ungolfed y Transpose rows and columns. mZ{ } Map each row Z by this function: Zî Fill Z with (no argument = zeroes). íZ Pair each item in the result with the corresponding item in Z. c Flatten into a single array. p0 Append another 0. 

Repeated twice, this process gives the desired output. The result is implicitly printed.

Husk, 12 bytes

₁₁ Tm»o:0:;0 

Takes and returns a 2D integer array. Try it online!

Explanation

Same idea as in many other answers: add zeroes to each row and transpose, twice. The row operation is implemented with a fold.

₁₁ Main function: apply first helper function twice Tm»o:0:;0 First helper function. m Map over rows: » Fold over row: o Composition of : prepend new value and :0 prepend zero, ;0 starting from [0]. This inserts 0s between and around elements. T Then transpose. 

Mathematica, 39 bytes

r=Riffle[#,0,{1,-1,2}]&/@Thread@#&;r@*r 

Try it at the Wolfram sandbox! Call it like "r=Riffle[#,0,{1,-1,2}]&/@Thread@#&;r@*r@{{1,2},{3,4}}".

Like many other answers, this works by transposing and riffling zeros in each row then doing the same thing again. Inspired by Jonathan Allan's Jelly answer specifically, but only because I happened to see that answer first.

Dyalog APL, 24 bytes

4 bytes saved thanks to @ZacharyT

5 bytes saved thanks to @KritixiLithos

{{⍵↑⍨-1+⍴⍵}⊃⍪/,/2 2∘↑¨⍵} 

Try it online!

Octave, 41 bytes

@(M)resize(kron(M,[0 0;0 1]),2*size(M)+1) 

Try it online!

Python 3, 104 101 97 93 86 bytes

• @Zachary T saved 3 bytes: unused variable w removed and one unwanted space
• @Zachary T saved yet another 4 bytes: [a,b] as just a,b while appending to a list
• @nore saved 4 bytes: use of slicing
• @Zachary T and @ovs helped saving 7 bytes: squeezing the statements in for loop

def f(a): m=[(2*len(a[0])+1)*[0]] for i in a:r=m[0][:];r[1::2]=i;m+=r,m[0] return m 

Try it online!

Python 3, 118 bytes

def a(b): z='00'*len(b[0])+'0' r=z+'\n' for c in b: e='0' for d in c:e+=str(d)+'0' r+=e+'\n'+z+'\n' return r 

First time golfing! Not the best, but I'm quite proud if I can say so myself!

• -17 bytes from Wheat comments
• -4 bytes from inlining the second for loop

Python 2, 64 bytes

lambda l:map(g,*map(g,*l)) g=lambda*l:sum([[x,0]for x in l],[0]) 

Try it online!

The function g intersperses the input between zeroes. The main function transposes the input while applying g, then does so again. Maybe there's a way to avoid the repetition in the main function.

R, 65 bytes

Thanks to Jarko Dubbeldam and Giuseppe for very valuable comments!

Code

f=function(x){a=dim(x);y=array(0,2*a+1);y[2*1:a[1],2*1:a[2]]=x;y} 

Input for the function must be a matrix or two dimensional array.

Test

f(matrix(1)) f(matrix(c(1,5,4,2),2)) f(matrix(c(1,4,7),1)) f(matrix(c(6,4,2))) 

Output

> f(matrix(1)) [,1] [,2] [,3] [1,] 0 0 0 [2,] 0 1 0 [3,] 0 0 0 > f(matrix(c(1,5,4,2),2)) [,1] [,2] [,3] [,4] [,5] [1,] 0 0 0 0 0 [2,] 0 1 0 4 0 [3,] 0 0 0 0 0 [4,] 0 5 0 2 0 [5,] 0 0 0 0 0 > f(matrix(c(1,4,7),1)) [,1] [,2] [,3] [,4] [,5] [,6] [,7] [1,] 0 0 0 0 0 0 0 [2,] 0 1 0 4 0 7 0 [3,] 0 0 0 0 0 0 0 > f(matrix(c(6,4,2))) [,1] [,2] [,3] [1,] 0 0 0 [2,] 0 6 0 [3,] 0 0 0 [4,] 0 4 0 [5,] 0 0 0 [6,] 0 2 0 [7,] 0 0 0 

Mathematica, 55 bytes

(a=ArrayFlatten)@{o={0,0},{0,a@Map[{{#,0},o}&,#,{2}]}}& 

PHP, 98 bytes

Input as 2D array, Output as string

<?foreach($_GET as$v)echo$r=str_pad(0,(count($v)*2+1)*2-1," 0")," 0 ".join(" 0 ",$v)." 0 ";echo$r; 

Try it online!

PHP, 116 bytes

Input and Output as 2D array

<?foreach($_GET as$v){$r[]=array_fill(0,count($v)*2+1,0);$r[]=str_split("0".join(0,$v)."0");}$r[]=$r[0];print_r($r); 

Try it online!

Clojure, 91 bytes

#(for[h[(/ 2)]i(range(- h)(count %)h)](for[j(range(- h)(count(% 0))h)](get(get % i[])j 0))) 

Iterates over ranges in half-steps.

Perl 6, 33 bytes

{map {0,|$_,0},0 xx$_,|$_,0 xx$_} 

Try it online!

JavaScript (ES6), 73 72 bytes

a=>(g=a=>(r=[b],a.map(v=>r.push(v,b)),b=0,r))(a,b=a[0].map(_=>0)).map(g) 

Formatted and commented

Inserting zeros horizontally and vertically are very similar operations. The idea here is to use the same function g() for both steps.

a => // a = input array (g = a => // g = function that takes an array 'a', ( // builds a new array 'r' where r = [b], // 'b' is inserted at the beginning a.map(v => r.push(v, b)), // and every two positions, b = 0, // sets b = 0 for the next calls r // and returns this new array ))(a, b = a[0].map(_ => 0)) // we first call 'g' on 'a' with b = row of zeros .map(g) // we then call 'g' on each row of the new array with b = 0 

Test cases

let f = a=>(g=a=>(r=[b],a.map(v=>r.push(v,b)),b=0,r))(a,b=a[0].map(_=>0)).map(g) console.log(JSON.stringify(f([ [1] ]))) console.log(JSON.stringify(f([ [1, 4], [5, 2] ]))) console.log(JSON.stringify(f([ [1, 4, 7] ]))) console.log(JSON.stringify(f([ [6], [4], [2] ])))

Charcoal, 49 bytes

Ａ⪪θ;αＡ””βＦ⁺¹×²Ｌ§α⁰Ａ⁺β⁰βＡ⁺β¶βＦα«βＡ0δＦιＡ⁺δ⁺κ⁰δ⁺䶻β 

Try it online!

The input is a single string separating the rows with a semicolon.

C++17 + Modules, 192 bytes

Input as rows of strings from cin, Output to cout

import std.core;int main(){using namespace std;int i;auto&x=cout;string s;while(getline(cin,s)){for(int j=i=s.length()*2+1;j--;)x<<0;x<<'\n';for(auto c:s)x<<'0'<<c;x<<"0\n";}for(;i--;)x<<'0';} 

C#, 146 bytes

Data

• Input Int32[,] m The matrix to be exploded
• Output Int32[,] The exploded matrix

Golfed

(int[,] m)=>{int X=m.GetLength(0),Y=m.GetLength(1),x,y;var n=new int[X*2+1,Y*2+1];for(x=0;x<X;x++)for(y=0;y<Y;y++)n[x*2+1,y*2+1]=m[x,y];return n;} 

Ungolfed

( int[,] m ) => { int X = m.GetLength( 0 ), Y = m.GetLength( 1 ), x, y; var n = new int[ X * 2 + 1, Y * 2 + 1 ]; for( x = 0; x < X; x++ ) for( y = 0; y < Y; y++ ) n[ x * 2 + 1, y * 2 + 1 ] = m[ x, y ]; return n; } 

Ungolfed readable

// Takes an matrix of Int32 objects ( int[,] m ) => { // To lessen the byte count, store the matrix size int X = m.GetLength( 0 ), Y = m.GetLength( 1 ), x, y; // Create the new matrix, with the new size var n = new int[ X * 2 + 1, Y * 2 + 1 ]; // Cycle through the matrix, and fill the spots for( x = 0; x < X; x++ ) for( y = 0; y < Y; y++ ) n[ x * 2 + 1, y * 2 + 1 ] = m[ x, y ]; // Return the exploded matrix return n; } 

Full code

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace TestBench { public static class Program { private static Func<Int32[,], Int32[,]> f = ( int[,] m ) => { int X = m.GetLength( 0 ), Y = m.GetLength( 1 ), x, y, a = X * 2 + 1, b = Y * 2 + 1; var n = new int[ a, b ]; for( x = 0; x < X; x++ ) for( y = 0; y < Y; y++ ) n[ a, b ] = m[ x, y ]; return n; }; public static Int32[,] Run( Int32[,] matrix ) { Int32[,] result = f( matrix ); Console.WriteLine( "Input" ); PrintMatrix( matrix ); Console.WriteLine( "Output" ); PrintMatrix( result ); Console.WriteLine("\n\n"); return result; } public static void RunTests() { Run( new int[,] { { 1 } } ); Run( new int[,] { { 1, 3, 5 } } ); Run( new int[,] { { 1 }, { 3 }, { 5 } } ); Run( new int[,] { { 1, 3, 5 }, { 1, 3, 5 }, { 1, 3, 5 } } ); } static void Main( string[] args ) { RunTests(); Console.ReadLine(); } public static void PrintMatrix<TSource>( TSource[,] array ) { PrintMatrix( array, o => o.ToString() ); } public static void PrintMatrix<TSource>( TSource[,] array, Func<TSource, String> valueFetcher ) { List<String> output = new List<String>(); for( Int32 xIndex = 0; xIndex < array.GetLength( 0 ); xIndex++ ) { List<String> inner = new List<String>(); for( Int32 yIndex = 0; yIndex < array.GetLength( 1 ); yIndex++ ) { inner.Add( valueFetcher( array[ xIndex, yIndex ] ) ); } output.Add( $"[ {String.Join( ", ", inner )} ]" ); } Console.WriteLine( $"[\n {String.Join( ",\n ", output )}\n]" ); } } } 

Releases

• v1.0 - 146 bytes - Initial solution.

Notes

• None

Java 8, 183 166 162 129 119 bytes

m->{int a=m.length,b=m[0].length,i=a*b,r[][]=new int[a-~a][b-~b];for(;i-->0;)r[i/b*2+1][i%b*2+1]=m[i/b][i%b];return r;} 

Input and output as a int[][].

-33 bytes by creating a port of @auhmaan's C# answer.
-10 bytes thanks to @ceilingcat.

Explanation:

Try it here.

m->{ // Method with integer-matrix as both parameter & return int a=m.length, // Set `a` to the input-height b=m[0].length, // Set `b` to the input-width i=a*b, // Index integer, starting at `a*b` r[][]=new int[a-~a][b-~b]; // Result integer-matrix with dimensions a*a+1 by b*b+1 for(;i-->0;) // Loop `i` in the range (a*b, 0] (so over each cell): r[i/b*2+1][i%b*2+1]= // Fill the current cell of the result-matrix: m[i/b][i%b]; // With the correct input-integers return r;} // Return result integer-matrix 

Dyalog APL, 24 bytes

{{⍵↑⍨¯1-⍴⍵}⊃⍪/,/2 2∘↑¨⍵} 

Any improvements are welcome and wanted!

Python 2, 92 bytes

n=input() a=[[0]*(2*len(n[0])+1)for i in[0]+2*n] for l,v in zip(a[1::2],n):l[1::2]=v print a 

Try it online!

Python 3 + Numpy, 87 bytes

from numpy import* def f(a):b=zeros((2*len(a)+1,2*len(a[0])+1));b[1::2,1::2]=a;return b 

Try it online!

JavaScript (ES6), 80 78 bytes

a=>[...a,...a,a[0]].map((b,i)=>[...b,...b,0].map((_,j)=>i&j&1&&a[i>>1][j>>1])) 

Pyth, 13 bytes

uCm+0s,R0dG2Q 

Demonstration

Another 13:

uC.iL+0m0dG2Q 

APL (Dyalog), 22 bytes

Prompts for matrix, returns enclosed matrix.

{⍺⍀⍵\a}/⍴∘0 1¨1+2×⍴a←⎕ 

Try it online!

a←⎕ prompt for matrix and assign to a

⍴ the dimensions of a (rows, columns)

2× multiply by two

1+ add one

⍴∘0 1¨ use each to reshape (cyclically) the numbers zero and one

{…}/ reduce by inserting the following anonymous function between the two numbers:

 ⍵\a expand* the columns of a according to the right argument

 ⍺⍀a expand* the rows of that according to the left argument

* 0 inserts a column/row of zeros, 1 inserts an original data column/row

J, 24 bytes

0,.0,[:,./^:2(0,.~,&0)"0 

Try it online!

05AB1E, 22 bytes

"vy0ý0.ø})"©.V€Sø®.Vø» 

Try it online!

Actually uses the same piece of code 2x, so I can store it as a string and use Eval for -10 bytes.