Concatenating 2 vectors into 1 vector with the values adjacent to each other

Question

Moey Rojas 2020-5-30

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评论： Star Strider 2020-5-31

Hi, I have a three vectors: month, year, and partial pressure of carbon dioxide for 2914 observations. I am trying to use a program to analyze the seasonality of the data, but the program requires that the data be in a 2914x2 (2914 rows, 2 columns) matrix such that column one is the year and month (i.e. February 2012 would be 20121 and June 1985 would be 19856) and column 2 is the partial pressure of carbon dioxide. I've tried countless times to get the data in this format but no matter what I do when I concatenate it forms a 2914x3 matrix. Is there a way to actually concatenate the year and month vectors to get in the format "yearmonth" like 20121 or 19856? Thanks so much!

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Moey Rojas 2020-5-30

Most of my code has been a derivative of yearmonthCO2=[yr, mon, pCO2]. What I'm trying to do is get a [yearmonth, pCO2] output.

Stephen23 2020-5-31

The best solution is to use datetime:

https://www.mathworks.com/help/matlab/ref/datetime.html

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Answer 1

Star Strider 2020-5-30

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编辑：Star Strider 2020-5-30

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Yes. Use datetime to create them.

Example —

CO2_Mtx = [2012 01 rand; 2012 2 rand; 1985 5 rand; 1985 6 rand];                                % Create Matrix
YM = datetime(num2str(CO2_Mtx(:,[1 2]),'%d %d'), 'InputFormat','yyyy MM', 'Format','yyyyMM');   % Convert ‘Years Month’ To ‘datetimeâ
CO2_Tbl = table(YM,CO2_Mtx(:,3), 'VariableNames',{'YearMth','CO2PP'})                           % Table Of Results

That should work with the data as you have described it. Without your actual matrix however, I cannot be certain.

Producing —

CO2_Tbl =
  4×2 table
    YearMth     CO2PP  
    _______    ________
    201201     0.046171
    201202     0.097132
    198505      0.82346
    198506      0.69483

EDIT —

Added ‘CO2_Tbl’ output.

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Tommy 2020-5-31

I think this is a great answer and I hope you don't delete it. I'm not quite at the point where I think datetime when I ought to, but I'm getting there, thanks in part to this answer - that's one of the main reasons I spend time on this site! I'd suggest the OP accept this answer.

Star Strider 2020-5-31

I decided to keep it posted!

The one glitch is that ‘PPCO2’ should have been ‘pCO2’. (And I was a Chemistry major!)

.

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Answer 2

Bjorn Gustavsson 2020-5-30

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Why not simply do something like this:

Year_pressure = [year(:) + (month(:)-.5)/12,p_CO2(:)];

Here I've modified your conversion of year+month to "fractional years", mainly because I dont understand how you can map February 2012 to 20121 and June 1985 to 19856, but you can simply replace what I did for the dates with whatever you need for converting the year-month to the format you require.

HTH

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Moey Rojas 2020-5-30

Thank you!

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Answer 3

Tommy 2020-5-30

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编辑：Tommy 2020-5-30

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Should February 2012 map to 20122 rather than 20121? If so, maybe this will do the trick?

month = repmat((1:12)', 5, 1);
year = repelem((1998:2002)', 12, 1);
pCO2 = rand(60, 1);
data = [str2num(sprintf('%d%d\n',[year,month]')), pCO2];

(edit)

>> fprintf('%d %0.3f\n',data')
19981 0.132
19982 0.085
19983 0.232
19984 0.625
19985 0.372
19986 0.130
19987 0.679
19988 0.836
19989 0.662
199810 0.815
199811 0.924
199812 0.314
19991 0.499
...