calculating the difference between daily precipitation values

hello i am shahidh and i have dataset like mentioned below

13.01.1941 07:30 4.1

14.01.1941 07:30 4.9

15.01.1941 07:30 4.9

16.01.1941 07:30 4.9

17.01.1941 07:30 4.9

18.01.1941 07:30 11.3

.

.

10.10.2021 07.30 23000

and i wated to calulate the daily value differences for this dataset and i wanted to plot the graph like on the x axis year and time) on y axis precipitation so does any one have an idea how to do that.

thank you

Answer 1

[Jon]

I am not sure how you are defining "daily value differences". If you want to know the difference between succesive values you can use MATLAB's diff function. So if you have a vector (e.g. your second column of data) of values x and want to know the change from one day to the next (assuming samples are taken on successive days) you could use

delta = diff(x)

Here is a little bit of example code that might give you some ideas about how to work with dates and times

% assign time values 
timevals = {'13.01.1941 07:30'
'14.01.1941 07:30'
'15.01.1941 07:30'
'16.01.1941 07:30'
'17.01.1941 07:30'
'18.01.1941 07:30'  };

% assign daily precipitation values
dailyPrecip = [ 4.1
4.9
4.9
4.9
4.9
11.3];

% convert times to MATLAB datetime vector
t = datetime(timevals,'InputFormat','dd.MM.yyyy hh:mm');

% find differences in daily rainfall amounts
delta = diff(dailyPrecip);

% plot result, note first delta corresponds to second day and so on
% so we start time at second day
figure
plot(t(2:end),delta); 

[Shahidh Shaik]

hello jon thank you very much for your answer it worked for the manual data but if i want to read the complete data set folder how can i do that for example it contains 28000 rows and 2 coulmns in the first column it contain dd.MM.yyyy hh:mm and second column it contain precipitation data.

[Jon]

I'm not sure what format your data file is in. If it is in a Excel Workbook .xlsx file or a .csv file you can use the following to import the data into a MATLAB table. So for example if your data were in a file called precipDat.xlsx

T = readtable('precipDat.xlsx')

if the data were in a file called precipDat.csv use:

T = readtable('precipDat.csv')

Assuming there are no headers, naming the columns this will give you a table with two columns called Var1 and Var2, you could then follow the original steps with a little modification.

t = datetime(T.Var1,'InputFormat','dd.MM.yyyy hh:mm');
delta = diff(T.Var2)
plot(t(2:end),delta)

You can get more info on the readtable command by typing doc readtable on the MATLAB command line.In particular if your data has headers you can import the data into a table with the columns named as they are in the data file. You can also skip intial rows and the like. I think you can see how to modify my example from that point, but let me know if you get stuck

[Jon]

Were you able to get this working. Did you have questions?