How to get the last two digits of a number?

Hello,

I have a table with 505 rows and 1 column. Each row contains a 4 digit number and from of these numbers I would like to extract the last two digits to add a second column to that table containing the last two digits of every number in the first column.

I would be grateful for any hints. Thank you

Answer 1

[David Fletcher]

x=4974

y=floor((x/100-floor(x/100))*100)

[Adam Danz]

+1 faster than mod

Comparison of the two methods

1000

rng(123) 
x = round(rand(5000,1)*10000);

n = 10000; 
t1 = tic;
cumulativeTime1 = nan(n,1);
for i = 1:n
   v = floor((x/100-floor(x/100))*100); 
   cumulativeTime1(i) = toc(t1); 
end

pause(1)

t2 = tic;
cumulativeTime2 = nan(n,1);
for i = 1:n
   w = mod(x,100);
   cumulativeTime2(i) = toc(t2); 
end

duration1 = diff(cumulativeTime1);
duration2 = diff(cumulativeTime2);

figure
hold on
plot(duration1,'DisplayName','floor')
plot(duration2,'DisplayName','mod')
xlabel('Iteration')
ylabel('time (sec)')
legend()

[Felician Putz]

Be careful with floor. This can give the wrong result for some numbers. Counter example: 1001, whose result is 0 for me because apparently floor(1.0000) is 0 for Matlab.

[Image Analyst]

floor(1.0000)

ans = 1

x = 1001; 
v = floor((x/100-floor(x/100))*100)

v = 0

fprintf('%.32f', (x/100-floor(x/100))*100) % This is not 1

0.99999999999997868371792719699442

https://matlab.fandom.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

Answer 2

[DGM]

Assuming they're integers:

% 10 rows random integers
n = (randi(8999,1,10)+1000)'

n = [n mod(n,100)]

If they aren't integers, you should decide how you want to round them first.

[Maximilian Lingel]

Thank you very much. Just one more question: How would you extract the first two digits of those 4 digit integers?

Thanks a lot.

[Adam Danz]

+1 I would have gone with mod, too.

[Adam Danz]

Either of the two existing solutions will work with 4-digit integers but note that if the 3rd digit is a 0 as in 4206, the extraction will be 6 and not 06 since matlab does not preserve the 0 place holder. If you want to retain the 0, you'll need to extract the digis as strings or character vectors.

Method 1: convert to string after extraction

rng(123) % for reprodicibility 
x = round(rand(10,1)*10000);
lastTwo = mod(x,100);
charVec = compose('%02d',lastTwo);     % for char-vectors
str = string(compose('%02d',mod(x,100))); % for string array

T = table(x, lastTwo, charVec, str)

T = 10×4 table
     x      lastTwo    charVec    str 
    ____    _______    _______    ____

    6965      65       {'65'}     "65"
    2861      61       {'61'}     "61"
    2269      69       {'69'}     "69"
    5513      13       {'13'}     "13"
    7195      95       {'95'}     "95"
    4231      31       {'31'}     "31"
    9808       8       {'08'}     "08"
    6848      48       {'48'}     "48"
    4809       9       {'09'}     "09"
    3921      21       {'21'}     "21"

Method 2: convert to string and then extract

rng(123) % for reprodicibility 
x = round(rand(10,1)*10000);
xstr = string(x); 
str = extractAfter(xstr,2); 
T = table(x, lastTwo, str)

T = 10×3 table
     x      lastTwo    str 
    ____    _______    ____

    6965      65       "65"
    2861      61       "61"
    2269      69       "69"
    5513      13       "13"
    7195      95       "95"
    4231      31       "31"
    9808       8       "08"
    6848      48       "48"
    4809       9       "09"
    3921      21       "21"