Converting HH:MM:SS into decimal days to make a time series

I need to make a timeseries across three days (7th June - 9th June 2010) - I'm unsure how to include both the time and days across the x-axis?

I think I need to convert into decimal days but I'm unsure on how to do this and combine both days and time.

Seperate timeseries plots need to be made for the mean phosphate and nitrate concentrations in surface and bottom waters, again I'm not sure how to do this!

Any help will be grateful, the excel sheet is attached.

[dpb]

Use the datetime type. plot is already aware of date axes with it.

Answer 1

[Cris LaPierre]

Use a datetime. When you plot, your data type is honored. You can use xtickformat to format how the data appears.

% Define date and time formats for import
opts = detectImportOptions("CTD12-17.xlsx");

% nice, but not necessary
opts.VariableNamingRule = "preserve";
opts = setvartype(opts,"Time","duration");
opts = setvaropts(opts,"Time","InputFormat","hh:mm:ss","DurationFormat","hh:mm:ss");

% Set datetime format for Date + Time
opts = setvartype(opts,"Date_TimeCombined","datetime");
opts = setvaropts(opts,"Date_TimeCombined","InputFormat","dd/MM/yy HH:mm:ss");

% Load data
data = readtable("CTD12-17.xlsx",opts)

data = 6x7 table
       Date          Time      Date + Time Combined    Bottom Water Mean N+N    Surface Water Mean N+N    Bottom Water Mean P    Surface Water Mean P
    ___________    ________    ____________________    _____________________    ______________________    ___________________    ____________________

    07-Jul-2010    04:55:00     07/07/10 04:55:00              10.24                     5.38                    0.68                    0.43        
    07-Jul-2010    15:06:38     07/07/10 15:06:38               8.77                     3.11                    0.64                     0.5        
    07-Jul-2010    22:21:32     07/07/10 22:21:32               9.86                     4.84                    9.67                    0.39        
    08-Jul-2010    04:12:44     08/07/10 04:12:44               9.86                     4.84                    0.67                    0.39        
    08-Jul-2010    20:31:47     08/07/10 20:31:47               9.81                      4.4                    0.71                    0.38        
    09-Jul-2010    02:35:24     09/07/10 02:35:24              10.46                     3.43                     0.7                    0.32        

%Plot
plot(data.("Date + Time Combined"),data.("Bottom Water Mean N+N"))

[emily bristow]

Hiya,

I'll give it a go, just wondering why the x-axis is July-Sep when my dates are only in July?

[Cris LaPierre]

Ah, because the Date+Time column format is incorrect. I specified it as MM/dd/yy but it is actually dd/MM/yy. I've updated and rerun my original post.

[emily bristow]

Okay, thank you thats brilliant!