diff --git a/doc/src/manual/noteworthy-differences.md b/doc/src/manual/noteworthy-differences.md index c87b30c05ac0e..20ba324c098e3 100644 --- a/doc/src/manual/noteworthy-differences.md +++ b/doc/src/manual/noteworthy-differences.md @@ -127,8 +127,9 @@ For users coming to Julia from R, these are some noteworthy differences: matrices, then `A * B` denotes a matrix multiplication in Julia, equivalent to R's `A %*% B`. In R, this same notation would perform an element-wise (Hadamard) product. To get the element-wise multiplication operation, you need to write `A .* B` in Julia. - * Julia performs matrix transposition using the `.'` operator and conjugated transposition using - the `'` operator. Julia's `A.'` is therefore equivalent to R's `t(A)`. + * Julia performs matrix transposition using the `transpose` function and conjugated transposition using + the `'` operator or the `adjoint` function. Julia's `transpose(A)` is therefore equivalent to R's `t(A)`. + Additionally a non-recursive transpose in Julia is provided by the `permutedims` function. * Julia does not require parentheses when writing `if` statements or `for`/`while` loops: use `for i in [1, 2, 3]` instead of `for (i in c(1, 2, 3))` and `if i == 1` instead of `if (i == 1)`. * Julia does not treat the numbers `0` and `1` as Booleans. You cannot write `if (1)` in Julia, @@ -149,7 +150,8 @@ For users coming to Julia from R, these are some noteworthy differences: * The [DataFrames package](https://github.com/JuliaStats/DataFrames.jl) provides data frames. * Generalized linear models are provided by the [GLM package](https://github.com/JuliaStats/GLM.jl). * Julia provides tuples and real hash tables, but not R-style lists. When returning multiple items, - you should typically use a tuple: instead of `list(a = 1, b = 2)`, use `(1, 2)`. + you should typically use a tuple or a named tuple: instead of `list(a = 1, b = 2)`, use `(1, 2)` + or `(a=1, b=2)`. * Julia encourages users to write their own types, which are easier to use than S3 or S4 objects in R. Julia's multiple dispatch system means that `table(x::TypeA)` and `table(x::TypeB)` act like R's `table.TypeA(x)` and `table.TypeB(x)`. @@ -167,13 +169,14 @@ For users coming to Julia from R, these are some noteworthy differences: * Julia's [`sum`](@ref), [`prod`](@ref), [`maximum`](@ref), and [`minimum`](@ref) are different from their counterparts in R. They all accept one or two arguments. The first argument is an iterable collection such as an array. If there is a second argument, then this argument indicates the - dimensions, over which the operation is carried out. For instance, let `A=[[1 2],[3 4]]` in Julia - and `B=rbind(c(1,2),c(3,4))` be the same matrix in R. Then `sum(A)` gives the same result as - `sum(B)`, but `sum(A, 1)` is a row vector containing the sum over each column and `sum(A, 2)` - is a column vector containing the sum over each row. This contrasts to the behavior of R, where - `sum(B,1)=11` and `sum(B,2)=12`. If the second argument is a vector, then it specifies all the - dimensions over which the sum is performed, e.g., `sum(A,[1,2])=10`. It should be noted that - there is no error checking regarding the second argument. + dimensions, over which the operation is carried out. For instance, let `A = [1 2; 3 4]` in Julia + and `B <- rbind(c(1,2),c(3,4))` be the same matrix in R. Then `sum(A)` gives the same result as + `sum(B)`, but `sum(A, dims=1)` is a row vector containing the sum over each column and `sum(A, dims=2)` + is a column vector containing the sum over each row. This contrasts to the behavior of R, where separate + `colSums(B)` and `rowSums(B)` functions provide these functionalities. If the `dims` keyword argument is a + vector, then it specifies all the dimensions over which the sum is performed, while retaining the + dimensions of the summed array, e.g. `sum(A, dims=(1,2)) == hcat(10)`. It should be noted that there is no + error checking regarding the second argument. * Julia has several functions that can mutate their arguments. For example, it has both [`sort`](@ref) and [`sort!`](@ref). * In R, performance requires vectorization. In Julia, almost the opposite is true: the best performing