How to get the last two digits of a number?

Question

Maximilian Lingel 2021-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/826570-how-to-get-the-last-two-digits-of-a-number

评论： Image Analyst 2022-1-22

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

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Answer 1

David Fletcher 2021-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/826570-how-to-get-the-last-two-digits-of-a-number#answer_696475

x=4974
y=floor((x/100-floor(x/100))*100)

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Felician Putz 2022-1-22

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 2022-1-22

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

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Answer 2

DGM 2021-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/826570-how-to-get-the-last-two-digits-of-a-number#answer_696480

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.

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Adam Danz 2021-5-10

+1 I would have gone with mod, too.

Adam Danz 2021-5-10

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"