LAMBDA_Examples

LAMBDA_EXAMPLES.txt

/*
A series of LAMBDA functions which we have found useful or used for examples while shipping LAMBDA
NOTE: All examples are provided as-is and meant to showcase the possibilites of what can be achieved
with LAMBDA in Excel.
*/



/*
    FUNCTION NAME: APPENDCOLS
    DESCRIPTION: Appends two arrays column wise
    ARGS:
        array1: The array to append columns from array2 to
        array2: The array to append to array1

    EXAMPLE: 
        =APPENDCOLS(SEQUENCE(10,2),SEQUENCE(10,2,11))
*/

APPENDCOLS =LAMBDA(array1, array2,
    LET(
        //name definitions
        array1Rows, ROWS(array1),
        array1Cols, COLUMNS(array1),
        array2Rows, ROWS(array2),
        array2Cols, COLUMNS(array2),
        rowLen, MAX(array1Rows, array2Rows),        
        colLen, array1Cols + array2Cols,
        newArray, SEQUENCE(rowLen, colLen),
        colIndex, MOD(newArray - 1, colLen) + 1,
        rowIndex, 1 + ((newArray - colIndex) / colLen),
        
        //create the combined array
        resultArray, IF(
            colIndex > array1Cols,
            INDEX(array2, rowIndex, colIndex - array1Cols),
            INDEX(array1, rowIndex, colIndex)
        ),
        
        //return the resultArray
        resultArray
    )
);

/*
    FUNCTION NAME: APPENDROWS
    DESCRIPTION: Appends two arrays row-wise
    ARGS:
        array1: The array to append rows from array2 to
        array2: The array to append to array1

    EXAMPLE: 
        =APPENDROWS(SEQUENCE(10), SEQUENCE(10, 1, 11))
*/
APPENDROWS =LAMBDA(array1, array2,
    LET(
        array1Rows, ROWS(array1),
        colIndex, SEQUENCE(, MAX(COLUMNS(array1), COLUMNS(array2))),
        rowIndex1, SEQUENCE(array1Rows + ROWS(array2)),
        rowIndex2, rowIndex1 - array1Rows,
        IF(
            rowIndex2 >= 1,
            INDEX(array2, rowIndex2, colIndex),
            INDEX(array1, rowIndex1, colIndex)
        )
    )
);

/*
    FUNCTION NAME: COUNTWORDS
    DESCRIPTION: Counts the number of words in a text string
    ARGS:
        text: The text to string to count words

    EXAMPLE: 
        =COUNTWORDS("The quick brown fox jumps over the lazy dog")
*/
COUNTWORDS =LAMBDA(text,
    LET(
        Trimmedtext, TRIM(text),
        TrimmedtextLength, LEN(Trimmedtext),
        WhiteSpaceSubstitution, SUBSTITUTE(Trimmedtext, " ", ""),
        TextLengthNoSpaces, LEN(WhiteSpaceSubstitution),
        TrimmedtextLength - TextLengthNoSpaces + 1
    )
);

/*
    FUNCTION NAME: PYTHAG
    DESCRIPTION: Calculates the hypotenuse (c) of a right-angle triangle
    ARGS:
        a: leg1 of the triangle
        b: leg2 of the triangle

    EXAMPLE: 
        =PYTHAG(3,4)
*/
PYTHAG =LAMBDA(a, b, 
    SQRT(SUMSQ(a, b)
    ));

/*
    FUNCTION NAME: TEXTREVERSE
    DESCRIPTION: Reverses a text string
    ARGS:
        string: The text string to reverse 

    EXAMPLE: 
        =TEXTREVERSE("The quick brown fox jumps over the lazy dog")
*/
TEXTREVERSE =LAMBDA(string,
    LET(
        stringLength, LEN(string),
        substring, RIGHT(string, stringLength - 1),
        firstChar, LEFT(string, 1),
        IF(LEN(string) = 0, string, TEXTREVERSE(substring) & firstChar)
    )
);

/*
    FUNCTION NAME: TIMECONVERSION
    DESCRIPTION: Converts a time from one timezone to another
    ARGS:
        inputTime: The time to convert
        timezone1: The timezone of the inputTime
        timezone2: The timezone to convert to
        NOTE: timezones accept strings which correspond to the timezones retrieved from Data Types
        look at TIMEOFFSET for the full list of definitions

    EXAMPLE: 
        =TIMECONVERSION(NOW(),"Pacific Time Zone", "Central Time Zone")
*/
TIMECONVERSION =LAMBDA(inputTime, timezone1, timezone2,
    LET(
        zone1Offset, TIMEOFFSET(timezone1),
        zone2Offset, TIMEOFFSET(timezone2),
        delta, zone1Offset - zone2Offset,
        timeDifference, TIME(ABS(delta), 0, 0),
        IF(delta < 0, inputTime + timeDifference, inputTime - timeDifference)
    )
);

/*
    FUNCTION NAME: TIMEOFFSET
    DESCRIPTION: Looks up a timezone and returns the corresponding offset from GMT
    ARGS:
        timezone: A time zone to look up the offset of 
        NOTE: timezones accept strings which correspond to the timezones retrieved from Data Types
        look at TIMEOFFSET for the full list of definitions

    EXAMPLE: 
        =TIMEOFFSET("Pacific Time Zone")
*/
TIMEOFFSET =LAMBDA(timezone,
    LET(
        KST, 9,
        PST, -8,
        EST, -5,
        CST_AS, 8,
        GMT, 0,
        CST_Cen, -6,
        IFS(
            timezone = "Pacific Time Zone",
            PST,
            timezone = "Eastern Time Zone",
            EST,
            timezone = "Korea Standard Time",
            KST,
            timezone = "China Standard Time",
            CST_AS,
            timezone = "Greenwich Mean Time Zone",
            GMT,
            timezone = "British Summer Time",
            GMT,
            timezone = "Central Time Zone",
            CST_Cen
        )
    )
);

/*
    FUNCTION NAME: IFBLANK
    DESCRIPTION: Checks if a value is blank and returns value_if_blank if it is
    ARGS:
        value: The value to check if it's blank
        value_if_blank: The value to return if a blank value is found

    EXAMPLE: 
        =IFBLANK(,"blankVal")
*/
IFBLANK =LAMBDA(value, value_if_blank, IF(ISBLANK(value),value_if_blank,value));

/*
    FUNCTION NAME: DROPCOL
    DESCRIPTION: Drops a column from an array
    ARGS:
        array: The array to drop a column from
        column: The index of the column to drop

    EXAMPLE: 
        =DROPCOL(SEQUENCE(10,3),3)
*/
DROPCOL =LAMBDA(array, column,
    MAKEARRAY(
        ROWS(array),
        COLUMNS(array) -1,
        LAMBDA(i, j, INDEX(array, i, IF(j <column, j, j+1)))
    ));

/*
    FUNCTION NAME: PRODUCTIF
    DESCRIPTION: Multiplies all values given that they pass a condition
    ARGS:
        values: The values to multiply given the met condition
        condition: A LAMBDA which takes one argument (a value) and should return a boolean
        if the condition is met

    EXAMPLE: 
        =PRODUCTIF(SEQUENCE(5), LAMBDA(value, IF(value>3, TRUE, FALSE)))
*/
PRODUCTIF =LAMBDA(values, condition, 
    REDUCE(1, values, LAMBDA(a, b, 
        IF(condition(b), a*b, a)
        )
    ));

/*
    FUNCTION NAME: CHOOSERAND
    DESCRIPTION: Returns an aray of random values from another array
    ARGS:
        array: The values to choose from
        [rows]: The number of rows to return, if omitted returns one value

    EXAMPLE: 
        =CHOOSERAND(SEQUENCE(50))
*/
CHOOSERAND =LAMBDA(array, [rows],
    MAKEARRAY(IFOMITTED(rows, 1), 1, LAMBDA(a, b, 
    LET(arrayLen, COUNTA(array),
        randIndex, RANDBETWEEN(1, arrayLen),
        value, INDEX(array, randIndex),
        value
    )
)));

/*
    FUNCTION NAME: IFOMITTED
    DESCRIPTION: Checks if an optional value is omitted and returns value_if_omitted if it is
    ARGS:
        value: The value to check if it is omitted
        value_if_omitted: The value to return if a the value is omitted

    EXAMPLE: 
        =IFOMITTED(,"omitted")
*/
IFOMITTED =LAMBDA(value, value_if_omitted,
    IF(ISOMITTED(value),
    value_if_omitted, value
    ));

Thanks for sharing these beautiful functions but I have a problem when I use volatile functions (today, now, cell,...) inside let, function tip doesn't show up and the system considers it as a name (not function).
Could you please let me know what is the solution?

HI,

I dont know how this works but i have a contribution that i would like to add.. and maybe have someoen who knows how this works to tidy it up, its a way not to have to have multiple neasted substitutes..
SUBSTITUTEMULTI = LAMBDA(text, old_text_vector, new_text_vector, LET( hitsperword, (LEN(text) - LEN(SUBSTITUTE(text, old_text_vector, ""))) / LEN(old_text_vector), hitinstance, SEQUENCE(MAX(hitsperword)), array, TRANSPOSE(hitinstance & LEFT(TRANSPOSE(SEQUENCE(COLUMNS(old_text_vector), MAX(hitsperword))), 0)), wordsarray, TRANSPOSE(old_text_vector) & LEFT(array, 0), replacearray, TRANSPOSE(new_text_vector) & LEFT(array, 0), wordlocations, IFERROR(FIND("♦", SUBSTITUTE(text, wordsarray, "♦", array)), 0), findvector, SORT( STRINGTOARRAY(TEXTJOIN("♦", 1, IF(wordlocations > 0, TEXT(wordlocations, "000") & wordsarray, "")), "♦") ), replacevector, MID( SORT(STRINGTOARRAY(TEXTJOIN("♦", 1, IF(wordlocations > 0, TEXT(wordlocations, "000") & replacearray, "")), "♦")), 4, MAX(LEN(new_text_vector)) ), wordvector, MID(findvector, 4, LEN(findvector) - 3), rownumber, SEQUENCE(ROWS(findvector)), startpositions, IF( rownumber = 1, 1, VALUE(LEFT(INDEX(findvector, rownumber - 1), 3)) + LEN(INDEX(wordvector, rownumber - 1)) ), endpositions, VALUE(LEFT(findvector, 3)) - 1, strings, MID(text, startpositions, endpositions - startpositions + 1), reststring, MID( text, MAX(endpositions) + LEN(INDEX(wordvector, MAX(rownumber))) + 1, LEN(text) - MAX(LEN(endpositions)) ), IF(ISERROR(reststring),text,TEXTJOIN("",1,strings&replacevector)&reststring) ) );

and that includes this:

STRINGTOARRAY = LAMBDA(source, sep, LET( source,substitute(source," ","╦"), seplen, LEN(sep), tilde, REPT("╬", seplen), lItems, SEQUENCE(IFERROR((LEN(source) - LEN(SUBSTITUTE(source, sep, ""))) / seplen, 1) + 1), pos, IF(lItems = 1, 1, FIND(tilde, SUBSTITUTE(source, sep, tilde, lItems - 1))), length, IFERROR(FIND(tilde, SUBSTITUTE(source, sep, tilde, lItems)), LEN(source)) + LEN(sep) - pos, substitute(TRIM(MID(SUBSTITUTE(source, sep, REPT(" ", seplen)), pos, length)),"╦"," ") ) );

Edit: first version was incorrect...

Here is an alternative to the LAMBDA function: TEXTREVERSE (suggested by Chris Gross)
It is much shorter than the original

/*
FUNCTION NAME: REVERSESTR
AUTHOR: Meni Porat
DESCRIPTION: Reverses a string
ARGUMENSTS:
string: text string to be reversed
EXAMPLE:
=REVERSESTR("four score and seven years ago")
*/

REVERSESTR =LAMBDA(string,
let(strlen,LEN(string),
IF(strlen=0,string,
CONCAT(MID(string,SEQUENCE(strlen,1,strlen,-1),1)))))

@chgrossMSFT
If you rename your file to .sql you get pretty good syntax highlighting

Or codefences with sql like

/*
    FUNCTION NAME: APPENDROWS
    DESCRIPTION: Appends two arrays row-wise
    ARGS:
        array1: The array to append rows from array2 to
        array2: The array to append to array1

    EXAMPLE: 
        =APPENDROWS(SEQUENCE(10), SEQUENCE(10, 1, 11))
*/
APPENDROWS =LAMBDA(array1, array2,
    LET(
        array1Rows, ROWS(array1),
        colIndex, SEQUENCE(, MAX(COLUMNS(array1), COLUMNS(array2))),
        rowIndex1, SEQUENCE(array1Rows + ROWS(array2)),
        rowIndex2, rowIndex1 - array1Rows,
        IF(
            rowIndex2 >= 1,
            INDEX(array2, rowIndex2, colIndex),
            INDEX(array1, rowIndex1, colIndex)
        )
    )
);

This is amazing, and is there a way to an array for processing? If I want to be able to embed the data below into the formula and not have to have that data on the sheet, is there a way to do it?: I want to write a function that interpolates the speed of sound. Would be amazing if I can do something like

'''
speed_of_sound = LAMBDA(temp,
LET(
temp, {32.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 120.0, 140.0, 160.0, 180.0},
sos, {4603, 4672, 4748, 4814, 4871, 4919, 4960, 4995, 5049, 5091, 5101, 5095},
idx = countif(temp, ">"&temp),
sos[idx]
)
'''