Function from_excel: Improving code

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Function from_excel

The code converts a string into ASCII codes and then combines the ASCII codes into a single number. There are alternative ways to implement this.

R Function charToRaw

charToRaw("ABC") # generates the ASCII Hex codes: 41 42 43 as.numeric(charToRaw("ABC")) # base 10 codes: 65 66 67

Note:

• character "A" is offset by 65 from 0, or 64 from 1;
• character "a" is offset by 97 from 0, or 96 from 1;
• getting the base 10 code starting with 1: as.numeric(charToRaw("ABC")) - 64;

R Code

as.numletter = function(x) { lapply(x, function(s) { tmp = as.numeric(charToRaw(s)); tmp = ifelse(tmp >= 97, tmp - 96, tmp - 64); return(tmp); }); }

Example:

x = c("ABC", "abc", "Abc"); codes = as.numletter(x);

Encoding of Result

It is a different question, if the result should be kept as an array of integer-codes; or to combine the codes to a single number: but this latter solution requires continuous conversions back and force!

Note:

• Exponentiation using "**" can easily introduce hidden errors, as both "*" and "**" are valid mathematical operators;

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Code in Other Functions

The function read_blocks (and possibly other functions) contains the following code: if(!is.null(startrow) & !all(is.numeric(startrow))) { startrow[!is.numeric(startrow)] <- from_excel(startrow[!is.numeric(startrow)]) startrow <- as.numeric(startrow) }

This code could be moved entirely to a helper function: as.numletter.list = function(x) { if( ! is.null(x) && ! all(is.numeric(x))) { isNotNum = ! is.numeric(x); x[isNotNum] = as.numletter(x[isNotNum]); x = as.numeric(x); # may be unnecessary; } return(x); }

Note:

• it uses the function as.numletter from the 1st post;
• the 2 functions can be merged or kept separate, depending on the use cases inside the package;
• the operator "&&" skips the evaluation of the 2nd token;
• as.numletter.list: all elements inside an array (vector) have the same type and all(is.numeric(x)) is NOT needed; only lists can have elements of different type: it may be useful to review this code;