logical-operators

Here is a vector a <- c(TRUE, FALSE, FALSE, NA, FALSE, TRUE, NA, FALSE, TRUE) I'd like a simple function that returns TRUE everytime there is a TRUE in "a", and FALSE everytime there is a FALSE or a NA in "a". The three following things do not work a == TRUE identical(TRUE, a) isTRUE(a) Here is a solution a[-which(is.na(a))] but it doesn't seem to be a straightforward and easy solution Is there another solution ? Here are some functions (and operators) I know: identical() isTRUE() is.na() na.rm() & | ! What are the other functions (operators, tips, whatever,...) that are useful to deal with

I am having trouble trying to understand how logical operators work in C. I already understand how the bit-level operators work, and I also know that logical operators treat nonzero arguments as representing TRUE and zero arguments as representing FALSE But say we have 0x65 && 0x55. I do not understand why and how this operations gives 0x01. I tried to convert it to binary, but I cannot figure out how it works dasblinkenlight The && is a logical AND (as opposed to & , which is a bitwise AND ). It cares only that its operands as zero/non-zero values. Zeros are considered false , while non-zeros

I have a couple of variables and I want to check the following condition (written out in words, then my failed attempt at bash scripting): if varA EQUALS 1 AND ( varB EQUALS "t1" OR varB EQUALS "t2" ) then do something done. And in my failed attempt, I came up with: if (($varA == 1)) && ( (($varB == "t1")) || (($varC == "t2")) ); then scale=0.05 fi Gilles What you've written actually almost works (it would work if all the variables were numbers), but it's not an idiomatic way at all. (…) parentheses indicate a subshell . What's inside them isn't an expression like in many other languages. It's

What is the difference between the & and && logical operators in MATLAB? The single ampersand & is the logical AND operator. The double ampersand && is again a logical AND operator that employs short-circuiting behaviour. Short-circuiting just means the second operand (right hand side) is evaluated only when the result is not fully determined by the first operand (left hand side) A & B (A and B are evaluated) A && B (B is only evaluated if A is true) Loren && and || take scalar inputs and short-circuit always. | and & take array inputs and short-circuit only in if/while statements. For

I reading this code , and have this line switch (!!up + !!left) { what is !! operator ? two logical NOT ? yes, it's two nots. !!a is 1 if a is non-zero and 0 if a is 0 You can think of !! as clamping, as it were, to {0,1} . I personally find the usage a bad attempt to appear fancy. You can imagine it like this: !(!(a)) If you do it step by step, this make sense result = !42; //Result = 0 result = !(!42) //Result = 1 because !0 = 1 This will return 1 with any number (-42, 4.2f, etc.) but only with 0 , this will happens result = !0; //Result = 1 result = !(!0) //result = 0 !! is a more-portable

This is the only place I've ever seen and , or and not listed as actual operators in C++. When I wrote up a test program in NetBeans, I got the red underlining as if there was a syntax error and figured the website was wrong, but it is NetBeans which is wrong because it compiled and ran as expected. I can see ! being favored over not but the readability of and && or seems greater than their grammatical brothers. Why do these versions of the logical operators exist and why does seemingly no one use it? Is this truly valid C++ or some sort of compatibility with C that was included with the