I am trying to write a programme in MATLAB to calculate the average monthly rainfalls of a large data set I have. I input data is in the form of a column of rainfall values for a number of years. The rainfall is collected on a daily basis but I am only interested in the average monthly rainfall. I need a programme to calculate this for me as it would take too long manually. This is what i have so far:
%Specify the number of columns of input data
col=1;
%Open the input file
fid = fopen('sum.txt','r');
X = fscanf(fid,'%g %g',[col inf]);
X = X';
fclose(fid);
%Define initial conditions
i=1989;
%current day
k=1;
%current month of year
j=0;
%months
p=0;
%number of days in month
D=0;
%Outer loop counts the years
while i<=1999;
i=i+1;
%Inner loop counts the months
while j<=12;
j=j+1; p=p+1; k=k+D;
%Determine the number of days in each month
if j==1  j==3  j==5  j==7  j==8  j==10  j==12
D=31;
%Determine if year is a leap year or not
else
if j==2 && rem(i,4)==0 && rem(i,100)~=0  rem(i,400)==0
D=29;
else
D=28;
if j==4  j==6 j==9  j==11
D=30;
end
end
end
end
end
%Calculate average monthly rainfalls
average(p) = (X(k) + X(k+D1))/D
it just does not work and I am really stuck.
Calculate average monthly rainfall in matlab
Page 1 of 13 Replies  11941 Views  Last Post: 10 February 2009  08:03 PM
Replies To: Calculate average monthly rainfall in matlab
#2
Re: Calculate average monthly rainfall in matlab
Posted 09 February 2009  06:10 PM
Can you post a sample of the data set, like ten rows?
#3
Re: Calculate average monthly rainfall in matlab
Posted 10 February 2009  02:59 AM
#4
Re: Calculate average monthly rainfall in matlab
Posted 10 February 2009  08:03 PM
Now, I don't have MATLAB on my computer, and, to be honest, nor have I ever used MATLAB, however I think the logic of this code should be clear enough for you to implement it yourself:
Keep in mind, though, that I do not have MATLAB, so I never tested this code. Therefore, you may recieve some syntax errors.
function l = isleapyear(year) % isleapyear(year) Returns 1 if the specified year % is a leap year % Is the year divisible by four? if rem(year, 4) == 0 l = 1 % Then the year is a leap year % Is the year a centenary year and is it divisible by 400? if (rem(year, 100) == 0 && rem(year, 400) == 0) l = 0; % Then the year isn't a leap year end else l = 0; % Not a leap year end function d = daysinmonth(month, year) % daysinmonth(month, year) Returns the number of days in % the given month of the given % year. The month is represented % by an integer between 1 and 12 % where 1 = Jan, 2 = Feb, 3 = Mar, % etc. if ((month == 1)  (month == 3)  (month == 5)  (month == 7)  (month == 8)  (month == 10)  (month == 12)) % January, March, May, June, July, August, d = 31; % October, and December all have 31 days elseif ((month == 4)  (month == 6)  (month == 9)  (month == 11)) % April, June, September, and November d = 30; % have 30 days elseif month == 2 if leapyear(year) % February has 29 days if it is a leap year d = 29; else % Otherwise, it has 28 days d = 28; end fid = fopen('sum.txt', 'r'); if(fid < 0) error('Couldn''t open sum.txt!'); end X = fscanf(fid, '%f'); fclose(fid); startmonth = 1; % The month of the first rainfall measurement in the data set startyear = 1989; endmonth = 8; % The month whose rainfall average we want to calculate endyear = 1990; % In this case, we want the average rainfall of August 1990 days = 0; % Days since startmonth of startyear month = startmonth; year = startyear; done = 0; % Determines if we should keep looping while year <= endyear && ~done while(month <= 12) if (month == endmonth) && (year == endyear) done = 1; break end days = days + daysinmonth(month, year); month = month + 1; end if ~done month = 1; year = year + 1; end end if done average = mean(X(days : days + (daysinmonth(endmonth, endyear)  1))); end
Keep in mind, though, that I do not have MATLAB, so I never tested this code. Therefore, you may recieve some syntax errors.
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