Re: Finding Max Value of Column in Multi-Dimesional Array
On Friday, 5 July 2019 at 19:56:54 UTC, ag0aep6g wrote: It works when you pass an actual callable instead, e.g. a lambda: p.map!(a => a[column]).maxElement.writeln; On Friday, 5 July 2019 at 20:22:14 UTC, dwdv wrote: Furthermore, Samir, the parameter `a` can be renamed to whatever you prefer or what fits the code at hand best, e.g. `(row => row[column])`, as opposed to the string version, where only a small set of mostly single character names is supported. Thank you very much for the explanation! As I've mentioned before, I have a lot to learn about the `map` function and the details provided here help immensely. Samir
Re: Finding Max Value of Column in Multi-Dimesional Array
On 7/5/19 9:56 PM, ag0aep6g via Digitalmars-d-learn wrote:
On 05.07.19 20:49, Samir wrote:
As a follow-on to my earlier question, is there a way to pass a
variable to the `map` function that specifies the column, rather than
hard-coding it? I'm thinking of something like:
p.map!("a[column]").maxElement.writeln;
You can't do that with the string style, because the string is turned
into a function inside of `map`. Your `column` isn't visible there.
It works when you pass an actual callable instead, e.g. a lambda:
p.map!(a => a[column]).maxElement.writeln;
Furthermore, Samir, the parameter `a` can be renamed to whatever you
prefer or what fits the code at hand best, e.g. `(row => row[column])`,
as opposed to the string version, where only a small set of mostly
single character names is supported.
Re: Finding Max Value of Column in Multi-Dimesional Array
On 7/5/19 9:56 PM, ag0aep6g via Digitalmars-d-learn wrote:
On 05.07.19 20:49, Samir wrote:
As a follow-on to my earlier question, is there a way to pass a
variable to the `map` function that specifies the column, rather than
hard-coding it? I'm thinking of something like:
p.map!("a[column]").maxElement.writeln;
You can't do that with the string style, because the string is turned
into a function inside of `map`. Your `column` isn't visible there.
It works when you pass an actual callable instead, e.g. a lambda:
p.map!(a => a[column]).maxElement.writeln;
Furthermore, Samir, the parameter `a` can be renamed to whatever you
prefer or what fits the code at hand best, e.g. `(row => row[column])`,
as opposed to the string version, where only a small set of mostly
single character names is supported.
Re: Finding Max Value of Column in Multi-Dimesional Array
On 05.07.19 20:49, Samir wrote:
As a follow-on to my earlier question, is there a way to pass a variable
to the `map` function that specifies the column, rather than hard-coding
it? I'm thinking of something like:
p.map!("a[column]").maxElement.writeln;
You can't do that with the string style, because the string is turned
into a function inside of `map`. Your `column` isn't visible there.
It works when you pass an actual callable instead, e.g. a lambda:
p.map!(a => a[column]).maxElement.writeln;
Re: Finding Max Value of Column in Multi-Dimesional Array
On Friday, 5 July 2019 at 00:54:15 UTC, Samir wrote:
Is there a cleaner way of finding the maximum value of say the
third column in a multi-dimensional array than this?
int[][] p = [[1,2,3,4], [9,0,5,4], [0,6,2,1]];
writeln([p[0][2], p[1][2], p[2][2]].max);
I've tried the following
writeln([0, 1, 2].map!(p[a][2]).max);
but get an "Error: undefined identifier a" error.
As a follow-on to my earlier question, is there a way to pass a
variable to the `map` function that specifies the column, rather
than hard-coding it? I'm thinking of something like:
p.map!("a[column]").maxElement.writeln;
In the mean time, I am looking further into Ilya's mir-algorithm
library.
Thanks
Samir
Re: Finding Max Value of Column in Multi-Dimesional Array
On Friday, 5 July 2019 at 01:41:38 UTC, 9il wrote: You may want to take a look into mir-algorithm [1] library. It contains ndsilce package [2] to work with multidimensional data. Thanks for referring me to this library, Ilya. I will have to check this out. While it seems a bit more complicated for my particular use case, this definitely seems like something worth checking out for future use! On Friday, 5 July 2019 at 03:02:29 UTC, Jordan Wilson wrote: p.map!"a[2]".maxElement.writeln; // 5 Thank you, Jordan. I think this is what I was looking for. I am still struggling to wrap my head around the use of `map` but these examples really help. Samir
Re: Finding Max Value of Column in Multi-Dimesional Array
On Friday, 5 July 2019 at 00:54:15 UTC, Samir wrote: Is there a cleaner way of finding the maximum value of say the third column in a multi-dimensional array than this? int[][] p = [[1,2,3,4], [9,0,5,4], [0,6,2,1]]; writeln([p[0][2], p[1][2], p[2][2]].max); I've tried the following writeln([0, 1, 2].map!(p[a][2]).max); but get an "Error: undefined identifier a" error. I know there doesn't seem to be much of a difference between two examples but my real-world array is more complex which is why I'm looking for a more scalable option. Thanks Samir p.map!(a => a[2]).maxElement.writeln; // 5 p.map!"a[2]".maxElement.writeln; // 5 Or, modifying your example: writeln([0,1,2].map!(a => p[a][2]).maxElement; Thanks, Jordan
Re: Finding Max Value of Column in Multi-Dimesional Array
On Friday, 5 July 2019 at 00:54:15 UTC, Samir wrote:
Is there a cleaner way of finding the maximum value of say the
third column in a multi-dimensional array than this?
int[][] p = [[1,2,3,4], [9,0,5,4], [0,6,2,1]];
writeln([p[0][2], p[1][2], p[2][2]].max);
I've tried the following
writeln([0, 1, 2].map!(p[a][2]).max);
but get an "Error: undefined identifier a" error.
I know there doesn't seem to be much of a difference between
two examples but my real-world array is more complex which is
why I'm looking for a more scalable option.
Thanks
Samir
Hi Samir,
You may want to take a look into mir-algorithm [1] library.
It contains ndsilce package [2] to work with multidimensional
data.
The following example can be run online [3]:
--
/+dub.sdl:
dependency "mir-algorithm" version="~>3.4.4"
+/
import mir.algorithm.iteration: reduce;
import mir.ndslice: fuse, map, byDim;
import mir.utility: max;
import std.stdio: writeln;
void main()
{
// create 2D matrix type of Slice!(int*, 2);
auto matrix = [[1,2,3,4], [9,0,5,4], [0,6,2,1]].fuse;
matrix
.byDim!1 // by columns
.map!(c => int.min.reduce!max(c))
.writeln; // [9, 6, 5, 4]
}
--
1. https://github.com/libmir/mir-algorithm
2. http://mir-algorithm.libmir.org/mir_ndslice.html
3. https://run.dlang.io/is/OW6zvF
Finding Max Value of Column in Multi-Dimesional Array
Is there a cleaner way of finding the maximum value of say the third column in a multi-dimensional array than this? int[][] p = [[1,2,3,4], [9,0,5,4], [0,6,2,1]]; writeln([p[0][2], p[1][2], p[2][2]].max); I've tried the following writeln([0, 1, 2].map!(p[a][2]).max); but get an "Error: undefined identifier a" error. I know there doesn't seem to be much of a difference between two examples but my real-world array is more complex which is why I'm looking for a more scalable option. Thanks Samir
