[UPDATE] add toString method.

README.md

@@ -406,6 +406,40 @@ For further subsequence documentation, see [compute-indexspace](https://github.c
 
 
 
+<a name="matrix-tostring"></a>
+#### mat.toString()
+
+Returns a `string` representation of a `Matrix`. This method is similar to [`Array#toString`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toString), except that rows are delineated by __semicolons__ and column values are delineated by __commas__.
+
+``` javascript
+var data = new Int8Array( 10 );
+for ( var i = 0; i < data.length; i++ ) {
+	data[ i ] = i;
+}
+
+var mat = matrix( data, [5,2] );
+
+var str = mat.toString();
+// 0,1;2,3;4,5;6,7;8,9
+```
+
+To construct an `array` of `arrays` from the `string` representation,
+
+``` javascript
+var rows,
+	cols,
+	i, j;
+
+rows = str.split( ';' );
+for ( i = 0; i < rows.length; i++ ) {
+	cols = rows[ i ].split( ',' );
+	rows[ i ] = new Array( cols.length );
+	for ( j = 0; j < cols.length; j++ ) {
+		rows[ i ][ j ] = parseFloat( cols[ j ] );
+	}	
+}
+```
+
 
 ===
 <a name="matrix-constructor"></a>

TODO.md

@@ -15,15 +15,16 @@ TODO
 			-	essentially an in-place map
 	-	`mset`, `mget`
 		-	use linear index
-5. `toString` method
-	-	`'a00,a01;a10,a11;a20,a21'` => use semicolons to demarcate rows
-6. `toArray` method (???)
+5. 
+6. 
 7. 
 8. should we allow negative indices for `iset`, `iget`, etc?
 9. 
 10. pretty print a matrix
 	-	separate module? => `compute-print-matrix`
 	-	does not seem essential to core functionality
+	- 	what about a general `print` module, which accepts `arrays`, `matrices`, `ndarrays`, and `dataframes`?
+		-	similar to `to-matrix`, `to-array`, etc.
 11. validate.io-matrix / validate.io-matrix-like
 12. benchmark fancy (subsequence) get versus normal `get`
 13. 

benchmark/b.toString.js

@@ -0,0 +1,60 @@
+'use strict';
+
+// MODULES //
+
+var matrix = require( './../lib' );
+
+
+// VARIABLES //
+
+var start,
+	stop,
+	iArr,
+	nRows,
+	nCols,
+	res,
+	len,
+	m, s,
+	i;
+
+
+// --------------------------------------
+// WARM-UP
+
+len = 1e6;
+for ( i = 0; i < len; i++ ) {
+	i = i;
+}
+
+
+// --------------------------------------
+// BENCHMARK
+
+len = 1e3;
+nRows = 128;
+nCols = 128;
+
+res = new Array( 1 );
+
+iArr = new Float64Array( nRows*nCols );
+for ( i = 0; i < nRows*nCols; i++ ) {
+	iArr[ i ] = i;
+}
+
+m = matrix( iArr, [nRows,nCols] );
+
+start = process.hrtime();
+for ( i = 0; i < len; i++ ) {
+	s = m.toString();
+}
+stop = process.hrtime( start );
+
+res[ 0 ] = stop[ 0 ] + stop[ 1 ]*1e-9;
+
+
+// --------------------------------------
+// RESULTS
+
+console.log( 'toString:\t%d ops/sec', Math.floor( len/res[ 0 ] ) );
+console.log( '\n' );
+

examples/index.js

@@ -14,3 +14,6 @@ mat.set( 1, 1, 5  );
 
 // Confirm that the matrix element was set:
 console.log( mat.get( 1, 1 ) );
+
+// Convert the matrix to a string:
+console.log( mat.toString() );

lib/ctor.js

@@ -100,6 +100,8 @@ Matrix.prototype.get = require( './get.js' );
 Matrix.prototype.iget = require( './iget.js' );
 Matrix.prototype.sget = require( './sget.js' );
 
+Matrix.prototype.toString = require( './toString.js' );
+
 
 // EXPORTS //
 

lib/ctor.raw.js

@@ -52,6 +52,8 @@ Matrix.prototype.get = require( './get.js' );
 Matrix.prototype.iget = require( './iget.js' );
 Matrix.prototype.sget = require( './sget.js' );
 
+Matrix.prototype.toString = require( './toString.js' );
+
 
 // EXPORTS //
 

lib/toString.js

@@ -0,0 +1,39 @@
+'use strict';
+
+/**
+* FUNCTION: toString()
+*	Returns a string representation of Matrix elements. Rows are delineated by semicolons. Column values are comma-delimited.
+*
+* @returns {String} string representation
+*/
+function toString() {
+	/* jshint validthis: true */
+	var nRows = this.shape[ 0 ],
+		nCols = this.shape[ 1 ],
+		s0 = this.strides[ 0 ],
+		s1 = this.strides[ 1 ],
+		m = nRows - 1,
+		n = nCols - 1,
+		str = '',
+		r,
+		i, j;
+
+	for ( i = 0; i < nRows; i++ ) {
+		r = i * s0;
+		for ( j = 0; j < nCols; j++ ) {
+			str += this.data[ r + j*s1 ];
+			if ( j < n ) {
+				str += ',';
+			}
+		}
+		if ( i < m ) {
+			str += ';';
+		}
+	}
+	return str;
+} // end FUNCTION toString()
+
+
+// EXPORTS //
+
+module.exports = toString;