JSL Programming Challenge: Convert from string of Ys and Ns to matrix of 1s and 0s, and back again

[#1]

Hi JSL programmers,

I had a little problem as part of a larger application and thought I'd share it with you, and see if there's a way to do it better/slicker.

Basically I have a vector of 1s and 0s (i.e. [1, 1, 0, 0, 1]) that I need to convert to a string of Ys and Ns (i.e. "YYNNY").  Then I need to do the reverse, that is convert a string of Ys and Ns back to a vector of 1s and 0s.

Here are my quick and dirty functions - let's see if you can come up with something beyond my feeble brainpower!

// Convert a vector of 1s and 0s to a string with no separators
matrix_10_to_yn = function({matrix_10}, {default local},
	yn_txt = "";
	if (nrows(matrix_10) > 0,
// Strip out square brackets and commas
		yn_txt = substitute(char(matrix_10), "[", "", "]", "", ", ", "");
// Now convert 1s to Y and 0s to N
		yn_txt = substitute(yn_txt, "1", "Y", "0", "N");
	);
	yn_txt;
);

// Convert a YN string with no separators to a vector of 1s and 0s 
yn_to_matrix_10 = function({yn_txt}, {default local},
	n = length(yn_txt);
	matrix_10 = j(n, 1, 0);
	for (i = 1, i <= n, i++,
		if (substr(yn_txt, i, 1) == "Y",
			matrix_10[i] = 1;
		);
	);
	matrix_10;
);

// Test thing out
a = yn_to_matrix_10("YYYNNNN"); show(a);
b = matrix_10_to_yn(a);			show(b);

c = yn_to_matrix_10("");		show(c);
d = matrix_10_to_yn(c);			show(d);

[#2 · Accepted solution]

Whatever works, works!  Here is one alternative.

exmat = J(25,1, RandomInteger(0,1));
exlst = Insert({}, {"Y", "N"}[2-exmat]);

convert_yn = Function({usr}, {rslt, ynList ={"Y","N"} },
 if(IsMatrix(usr), 
	rslt = insert({},ynList[2-usr])
 , //else
     rslt = J(nitems(usr),1, 1);
     rslt[loc(usr,"N")]=0
  );  //end if
  rslt
); //end Function

show(exmat, convert_yn(exmat), exlst, convert_yn(exlst));

[#3 · Accepted solution]

Another!!

Names Default to here(1);
yto1 = function({str}, 
	{DEFAULT LOCAL}, 
	list = words(str, "");
	design(list, {"Y"});
);
oneToY = function({mat}, 
	list = substitute(as list(mat), 1, "Y", 0, "N");
	Concat items(list, "");
);
str = "YYYNNNNYYNY";
nums = yto1(str);
show(nums);
str2 = oneToY(nums);
show(str2, str2==str);

[#4 · Accepted solution]

This won't extend to three values or missing/error values without some extra effort. It converts string--blob--matrix and does the Y and N detection using the number of the ASCII character in the matrix. The BlobToMatrix and MatrixToBlob functions are told to use 1-byte little-endian integers. The endianness is not critical for 1-byte numbers, big works just as well. It does depend on the characters having one byte representations. 

source = "YYNNYQ";
// if you are uncomfortable with hard coded constants...
Yvalue = Blob To Matrix( Char To Blob( "Y" ), "int", 1, "little" )[1]; // 89
Nvalue = Blob To Matrix( Char To Blob( "N" ), "int", 1, "little" )[1]; // 78
// forward
numbers = Blob To Matrix( Char To Blob( source ), "int", 1, "little" ) == Yvalue;
// reverse
string = Blob To Char( Matrix To Blob( Nvalue + numbers * (Yvalue - Nvalue), "int", 1, "little" ) );
// display
Show( source, numbers, string );

source = "YYNNYQ";
numbers = [1, 1, 0, 0, 1, 0];
string = "YYNNYN";

[#5 · Accepted solution]

you can do the string to matrix conversion in a single line using Char to Blob and Blob to Matrix. My contribution: 

names default to here(1);

a=[1,0, 1, 1, 1, 0, 0, 1, 0, 1];
b="YNYYYNNYNY";

f_YNString_to_IndicatorVector=Function({s},
	blob to matrix(char to blob(d),"int", 1, "little", 1)==89;
);

f_IndicatorVector_to_YNString=Function({v},{vv},
	vv=As List(v);
	vv[loc(v)]="Y";
	vv[loc(!v)]="N";
	concat items(vv,"");
);

show(a);
show(b);
Show(f_YNString_to_IndicatorVector(b));
Show(f_IndicatorVector_to_YNString(a));
Show(f_IndicatorVector_to_YNString(f_YNString_to_IndicatorVector(b)));

[#6]

Oops, I didn't see Craig's reply...his version is better, I think.

[#7]

Wow these are amazing.  Thanks all!

[#8]

and now I need to study the design() function!

[#9]

@pmroz, 
         Here is my take/attempt at this. Thanks for offering this interesting challenge. I know I am using a loop which I don't know if it will scale well over large matrices, but I thought, some others in the community can come up with a faster way. 

Clear Log(); Clear Globals(); 

ex = Associative Array({1,0} ,{"Y", "N"});

Test = [1,0, 1, 1, 1, 0, 0, 1, 0, 1];

Res = {}; 

for(i = 1, i <= N Rows(Test), i++,
		Insert Into(Res, ex << Get Value(Test[i])); 
   ); 

Show(Res);

[#10]

I use a generic 'mapply' function in most projects, so normally I would only need the last two lines:

Names Default to here(1);

// Utility function to make for loops, combo 'map' and 'apply'
// this is a 'fake' map/apply function because it allows side
// effects (like apply) and it also returns a value (like map)
mapply = function( {x, foo, arg1 = "__missing", arg2 = "__missing"}, { i, r = {}, x, foo, arg1, arg2, arg1missing, arg2missing },
	if( N Items( x ) < 1,
		return({}), //empty list supplied, return an empty list
		for( i = 1, i <= N Items(x), i++,
			arg1missing = 0; arg2missing = 0;
			If( type(arg1) == "String", If( arg1 == "__missing", arg1missing = 1 ) );
			If( type(arg2) == "String", If( arg2 == "__missing", arg2missing = 1 ) );
			if( 
				arg1missing == 1,
				r = Insert( r, foo( x[i] ) ),
				arg2missing == 1,
				r = Insert( r, foo( x[i], arg1 ) ),
				r = Insert( r, foo( x[i], arg1, arg2 ) )
			)
		)
	);
	return(r);
);

// Solution:
str = "YYYNNNNYYNY";
(numbers = mapply( words(str,""), function( {x}, if( x=="Y", 1, 0) ) ) )
mapply( as list(numbers), function( {x}, if( x==1,"Y", "N") ) )