I want to write a code in MATLAB that converts a letter into NATO alphabet. Such as the word 'hello' would be re-written as Hotel-Echo-Lima-Lima-Oscar. I have been having some trouble with the code. So far I have the following:
function natoText = textToNato(plaintext)
plaintext = lower(plaintext);
r = zeros(1, length(plaintext))
%Define my NATO alphabet
natalph = ["Alpha","Bravo","Charlie","Delta","Echo","Foxtrot","Golf", ...
"Hotel","India","Juliet","Kilo","Lima","Mike","November","Oscar", ...
"Papa","Quebec","Romeo","Sierra","Tango","Uniform","Victor",...
"Whiskey","Xray","Yankee","Zulu"];
%Define the normal lower alphabet
noralpha = ['a' : 'z'];
%Now we need to make a loop for matlab to check for each letter
for i = 1:length(text)
for j = 1:26
n = r(i) == natalph(j);
if noralpha(j) == text(i) : n
else r(i) = r(i)
natoText = ''
end
end
end
for v = 1:length(plaintext)
natoText = natoText + r(v) + ''
natoText = natoText(:,-1)
end
end
I know the above code is a mess and I am a bit in doubt what really I have been doing. Is there anyone who knows a better way of doing this? Can I modify the above code so that it works?
It is because now when I run the code, I am getting an empty plot, which I don't know why because I have not asked for a plot in any lines.
You can actually do your conversion in one line. Given your string array natalph:
plaintext = 'hello'; % Your input; could also be "hello"
natoText = strjoin(natalph(char(lower(plaintext))-96), '-');
And the result:
natoText =
string
"Hotel-Echo-Lima-Lima-Oscar"
This uses a trick that character arrays can be treated as numeric arrays of their ASCII equivalent values. The code char(lower(plaintext))-96 converts plaintext to lowercase, then to a character array (if it isn't already) and implicitly converts it to a numeric vector of ASCII values by subtracting 96. Since 'a' is equal to 97, this creates an index vector containing the values 1 ('a') through 26 ('z'). This is used to index the string array natalph, and these are then joined together with hyphens.
Related
I found this challenge:
Using your language, have the function LetterChanges(str) take the str parameter being passed and modify it using the following algorithm. Replace every letter in the string with the letter following it in the alphabet (ie. c becomes d, z becomes a). Then capitalize every vowel in this new string (a, e, i, o, u) and finally return this modified string.
I am new in Julia, and I was challenging myself in this challenge. I found this challenge very hard in Julia lang and I could not find a solution.
Here I tried to solve in the way below, but I got error: the x value is not defined
How would you solve this?
function LetterChanges(stringis::AbstractString)
alphabet = "abcdefghijklmnopqrstuvwxyz"
vohels = "aeiou"
for Char(x) in split(stringis, "")
if x == 'z'
x = 'a'
elseif x in vohels
uppercase(x)
else
Int(x)+1
Char(x)
println(x)
end
end
end
Thank you
As a side note:
The proposed solution works properly. However, if you would need high performance (which you probably do not given the source of your problem) it is more efficient to use string builder:
function LetterChanges2(str::AbstractString)
v = Set("aeiou")
#sprint(sizehint=sizeof(str)) do io # use on Julia 0.7 - new keyword argument
sprint() do io # use on Julia 0.6.2
for c in str
c = c == 'z' ? 'a' : c+1 # we assume that we got only letters from 'a':'z'
print(io, c in v ? uppercase(c) : c)
end
end
end
it is over 10x faster than the above.
EDIT: for Julia 0.7 this is a bit faster:
function LetterChanges2(str::AbstractString)
v = BitSet(collect(Int,"aeiouy"))
sprint(sizehint=sizeof(str)) do io # use on Julia 0.7 - new keyword argument
for c in str
c = c == 'z' ? 'a' : c+1 # we assume that we got only letters from 'a':'z'
write(io, Int(c) in v ? uppercase(c) : c)
end
end
end
There is a logic error. It says "Replace every letter in the string with the letter following it in the alphabet. Then capitalize every vowel in this new string". Your code checks, if it is a vowel. Then it capitalizes it or replaces it. That's different behavior. You have to first replace and then to check if it is a vowel.
You are replacing 'a' by 'Z'. You should be replacing 'z' by 'a'
The function split(stringis, "") returns an array of strings. You can't store these strings in Char(x). You have to store them in x and then you can transform theses string to char with c = x[1].
After transforming a char you have to store it in the variable: c = uppercase(c)
You don't need to transform a char into int. You can add a number to a char: c = c + 1
You have to store the new characters in a string and return them.
function LetterChanges(stringis::AbstractString)
# some code
str = ""
for x in split(stringis, "")
c = x[1]
# logic
str = "$str$c"
end
return str
end
Here's another version that is a bit faster than #BogumilKaminski's answer on version 0.6, but that might be different on 0.7. On the other hand, it might be a little less intimidating than the do-block magic ;)
function changeletters(str::String)
vowels = "aeiouy"
carr = Vector{Char}(length(str))
i = 0
for c in str
newchar = c == 'z' ? 'a' : c + 1
carr[i+=1] = newchar in vowels ? uppercase(newchar) : newchar
end
return String(carr)
end
At the risk of being accused of cheating, this is a dictionary-based approach:
function change_letters(s::String)::String
k = collect('a':'z')
v = vcat(collect('b':'z'), 'A')
d = Dict{Char, Char}(zip(k, v))
for c in Set("eiou")
d[c - 1] = uppercase(d[c - 1])
end
b = IOBuffer()
for c in s
print(b, d[c])
end
return String(take!(b))
end
It seems to compare well in speed terms with the other Julia 0.6 methods for long strings (e.g. 100,000 characters). There's a bit of unnecessary overhead in constructing the dictionary which is noticeable on small strings, but I'm far too lazy to type out the 'a'=>'b' construction long-hand!
when I run this codes the output is (" "," "),however it should be ("I","love")!!!, and there is no errors . what should I do to fix it ??
sen="I love dogs"
function Longest_word(sen)
x=" "
maxw=" "
minw=" "
minl=1
maxl=length(sen)
p=0
for i=1:length(sen)
if(sen[i]!=" ")
x=[x[1]...,sen[i]...]
else
p=length(x)
if p<min1
minl=p
minw=x
end
if p>maxl
maxl=p
maxw=x
end
x=" "
end
end
return minw,maxw
end
As #David mentioned, another and may be better solution can be achieved by using split function:
function longest_word(sentence)
sp=split(sentence)
len=map(length,sp)
return (sp[indmin(len)],sp[indmax(len)])
end
The idea of your code is good, but there are a few mistakes.
You can see what's going wrong by debugging a bit. The easiest way to do this is with #show, which prints out the value of variables. When code doesn't work like you expect, this is the first thing to do -- just ask it what it's doing by printing everything out!
E.g. if you put
if(sen[i]!=" ")
x=[x[1]...,sen[i]...]
#show x
and run the function with
Longest_word("I love dogs")
you will see that it is not doing what you want it to do, which (I believe) is add the ith letter to the string x.
Note that the ith letter accessed like sen[i] is a character not a string.
You can try converting it to a string with
string(sen[i])
but this gives a Unicode string, not an ASCII string, in recent versions of Julia.
In fact, it would be better not to iterate over the string using
for i in 1:length(sen)
but iterate over the characters in the string (which will also work if the string is Unicode):
for c in sen
Then you can initialise the string x as
x = UTF8String("")
and update it with
x = string(x, c)
Try out some of these possibilities and see if they help.
Also, you have maxl and minl defined wrong initially -- they should be the other way round. Also, the names of the variables are not very helpful for understanding what should happen. And the strings should be initialised to empty strings, "", not a string with a space, " ".
#daycaster is correct that there seems to be a min1 that should be minl.
However, in fact there is an easier way to solve the problem, using the split function, which divides a string into words.
Let us know if you still have a problem.
Here is a working version following your idea:
function longest_word(sentence)
x = UTF8String("")
maxw = ""
minw = ""
maxl = 0 # counterintuitive! start the "wrong" way round
minl = length(sentence)
for i in 1:length(sentence) # or: for c in sentence
if sentence[i] != ' ' # or: if c != ' '
x = string(x, sentence[i]) # or: x = string(x, c)
else
p = length(x)
if p < minl
minl = p
minw = x
end
if p > maxl
maxl = p
maxw = x
end
x = ""
end
end
return minw, maxw
end
Note that this function does not work if the longest word is at the end of the string. How could you modify it for this case?
I would like to read a data file with a Fortran program, where each line is a list of integers.
Each line has a variable number of integers, separated by a given character (space, comma...).
Sample input:
1,7,3,2
2,8
12,44,13,11
I have a solution to split lines, which I find rather convoluted:
module split
implicit none
contains
function string_to_integers(str, sep) result(a)
integer, allocatable :: a(:)
integer :: i, j, k, n, m, p, r
character(*) :: str
character :: sep, c
character(:), allocatable :: tmp
!First pass: find number of items (m), and maximum length of an item (r)
n = len_trim(str)
m = 1
j = 0
r = 0
do i = 1, n
if(str(i:i) == sep) then
m = m + 1
r = max(r, j)
j = 0
else
j = j + 1
end if
end do
r = max(r, j)
allocate(a(m))
allocate(character(r) :: tmp)
!Second pass: copy each item into temporary string (tmp),
!read an integer from tmp, and write this integer in the output array (a)
tmp(1:r) = " "
j = 0
k = 0
do i = 1, n
c = str(i:i)
if(c == sep) then
k = k + 1
read(tmp, *) p
a(k) = p
tmp(1:r) = " "
j = 0
else
j = j + 1
tmp(j:j) = c
end if
end do
k = k + 1
read(tmp, *) p
a(k) = p
deallocate(tmp)
end function
end module
My question:
Is there a simpler way to do this in Fortran? I mean, reading a list of values where the number of values to read is unknown. The above code looks awkward, and file I/O does not look easy in Fortran.
Also, the main program has to read lines with unknown and unbounded length. I am able to read lines if I assume they are all the same length (see below), but I don't know how to read unbounded lines. I suppose it would need the stream features of Fortran 2003, but I don't know how to write this.
Here is the current program:
program read_data
use split
implicit none
integer :: q
integer, allocatable :: a(:)
character(80) :: line
open(unit=10, file="input.txt", action="read", status="old", form="formatted")
do
read(10, "(A80)", iostat=q) line
if(q /= 0) exit
if(line(1:1) /= "#") then
a = string_to_integers(line, ",")
print *, ubound(a), a
end if
end do
close(10)
end program
A comment about the question: usually I would do this in Python, for example converting a line would be as simple as a = [int(x) for x in line.split(",")], and reading a file is likewise almost a trivial task. And I would do the "real" computing stuff with a Fortran DLL. However, I'd like to improve my Fortran skills on file I/O.
I don't claim it is the shortest possible, but it is much shorter than yours. And once you have it, you can reuse it. I don't completely agree with these claims how Fotran is bad at string processing, I do tokenization, recursive descent parsing and similar stuff just fine in Fortran, although it is easier in some other languages with richer libraries. Sometimes you can use the libraries written in other languages (especially C and C++) in Fortran too.
If you always use the comma you can remove the replacing by comma and thus shorten it even more.
function string_to_integers(str, sep) result(a)
integer, allocatable :: a(:)
character(*) :: str
character :: sep
integer :: i, n_sep
n_sep = 0
do i = 1, len_trim(str)
if (str(i:i)==sep) then
n_sep = n_sep + 1
str(i:i) = ','
end if
end do
allocate(a(n_sep+1))
read(str,*) a
end function
Potential for shortening: view the str as a character array using equivalence or transfer and use count() inside of allocate to get the size of a.
The code assumes that there is just one separator between each number and there is no separator before the first one. If multiple separators are allowed between two numbers, you have to check whether the preceding character is a separator or not
do i = 2, len_trim(str)
if (str(i:i)==sep .and. str(i-1:i-1)/=sep) then
n_sep = n_sep + 1
str(i:i) = ','
end if
end do
My answer is probably too simplistic for your goals but I have spent a lot of time recently reading in strange text files of numbers. My biggest problem is finding where they start (not hard in your case) then my best friend is the list-directed read.
read(unit=10,fmt=*) a
will read in all of the data into vector 'a', done deal. With this method you will not know which line any piece of data came from. If you want to allocate it then you can read the file once and figure out some algorithm to make the array larger than it needs to be, like maybe count the number of lines and you know a max data amount per line (say 21).
status = 0
do while ( status == 0)
line_counter = line_counter + 1
read(unit=10,, iostat=status, fmt=*)
end do
allocate(a(counter*21))
If you want to then eliminate zero values you can remove them or pre-seed the 'a' vector with a negative number if you don't expect any then remove all of those.
Another approach stemming from the other suggestion is to first count the commas then do a read where the loop is controlled by
do j = 1, line_counter ! You determined this on your first read
read(unit=11,fmt=*) a(j,:) ! a is now a 2 dimensional array (line_counter, maxNumberPerLine)
! You have a separate vector numberOfCommas(j) from before
end do
And now you can do whatever you want with these two arrays because you know all the data, which line it came from, and how many data were on each line.
I'm trying to do a library in Lua with some function that manipulate strings.
I want to do a function that changes the letter case to upper only on odd characters of the word.
This is an example:
Input: This LIBRARY should work with any string!
Result: ThIs LiBrArY ShOuLd WoRk WiTh AnY StRiNg!
I tried with the "gsub" function but i found it really difficult to use.
This almost works:
original = "This LIBRARY should work with any string!"
print(original:gsub("(.)(.)",function (x,y) return x:upper()..y end))
It fails when the string has odd length and the last char is a letter, as in
original = "This LIBRARY should work with any strings"
I'll leave that case as an exercise.
First, split the string into an array of words:
local original = "This LIBRARY should work with any string!"
local words = {}
for v in original:gmatch("%w+") do
words[#words + 1] = v
end
Then, make a function to turn words like expected, odd characters to upper, even characters to lower:
function changeCase(str)
local u = ""
for i = 1, #str do
if i % 2 == 1 then
u = u .. string.upper(str:sub(i, i))
else
u = u .. string.lower(str:sub(i, i))
end
end
return u
end
Using the function to modify every words:
for i,v in ipairs(words) do
words[i] = changeCase(v)
end
Finally, using table.concat to concatenate to one string:
local result = table.concat(words, " ")
print(result)
-- Output: ThIs LiBrArY ShOuLd WoRk WiTh AnY StRiNg
Since I am coding mostly in Haskell lately, functional-ish solution comes to mind:
local function head(str) return str[1] end
local function tail(str) return substr(str, 2) end
local function helper(str, c)
if #str == 0 then
return ""
end
if c % 2 == 1 then
return toupper(head(str)) .. helper(tail(str),c+1)
else
return head(str) .. helper(tail(str), c+1)
end
end
function foo(str)
return helper(str, 1)
end
Disclaimer: Not tested, just showing the idea.
And now for real, you can treat a string like a list of characters with random-access with reference semantics on []. Simple for loop with index should do the trick just fine.
I have a string (eg. 'STA') and I want to make a cell array that will be a concatenation of my sting with a numbers from 1 to X.
I want the code to do something like the fore loop here below:
for i = 1:Num
a = [{a} {strcat('STA',num2str(i))}]
end
I want the end results to be in the form of {<1xNum cell>}
a = 'STA1' 'STA2' 'STA3' ...
(I want to set this to a uitable in the ColumnFormat array)
ColumnFormat = {{a},... % 1
'numeric',... % 2
'numeric'}; % 3
I'm not sure about starting with STA1, but this should get you a list that starts with STA (from which I guess you could remove the first entry).
N = 5;
[X{1:N+1}] = deal('STA');
a = genvarname(X);
a = a(2:end);
You can do it with combination of NUM2STR (converts numbers to strings), CELLSTR (converts strings to cell array), STRTRIM (removes extra spaces)and STRCAT (combines with another string) functions.
You need (:) to make sure the numeric vector is column.
x = 1:Num;
a = strcat( 'STA', strtrim( cellstr( num2str(x(:)) ) ) );
As an alternative for matrix with more dimensions I have this helper function:
function c = num2cellstr(xx, varargin)
%Converts matrix of numeric data to cell array of strings
c = cellfun(#(x) num2str(x,varargin{:}), num2cell(xx), 'UniformOutput', false);
Try this:
N = 10;
a = cell(1,N);
for i = 1:N
a(i) = {['STA',num2str(i)]};
end