Hello, I have a table contains the calendar day of the year and 24-hour frequency. How to get daily max, min, and average temperature from the table?

[Star Strider]

A relatively straightforward way is to use table2timetable and then retime. The year-month-day information is a bit ambiguous (at least in the sample provided), so you may need to specify it in an options structure created by the detectImportOptions function.

Answer 1

[Voss]

Here's one approach:

% a table similar to yours, with only a few days, and only the relevant columns:
t = table(repelem({'2005-01-01'; '2005-02-01'; '2005-03-01'},96,1),-12.35+0.1*(1:288).','VariableNames',{'DAY','AIR_TEMP_DEG_C'})

t = 288×2 table
         DAY          AIR_TEMP_DEG_C
    ______________    ______________

    {'2005-01-01'}        -12.25    
    {'2005-01-01'}        -12.15    
    {'2005-01-01'}        -12.05    
    {'2005-01-01'}        -11.95    
    {'2005-01-01'}        -11.85    
    {'2005-01-01'}        -11.75    
    {'2005-01-01'}        -11.65    
    {'2005-01-01'}        -11.55    
    {'2005-01-01'}        -11.45    
    {'2005-01-01'}        -11.35    
    {'2005-01-01'}        -11.25    
    {'2005-01-01'}        -11.15    
    {'2005-01-01'}        -11.05    
    {'2005-01-01'}        -10.95    
    {'2005-01-01'}        -10.85    
    {'2005-01-01'}        -10.75    

% group the DAYs together:
[g, g_id] = findgroups(t.DAY);

% (g_id contains your days, if you should need it:)
g_id

g_id = 3×1 cell array
    {'2005-01-01'}
    {'2005-02-01'}
    {'2005-03-01'}

% find the min, max, and mean of AIR_TEMP_DEG_C for each DAY:
[min_all, max_all, mean_all] = splitapply(@get_min_max_mean, t.AIR_TEMP_DEG_C, g)

min_all = 3×1

-12.2500 -2.6500 6.9500

max_all = 3×1

-2.7500 6.8500 16.4500

mean_all = 3×1

-7.5000 2.1000 11.7000

function [min_val, max_val, mean_val] = get_min_max_mean(in)
min_val = min(in);
max_val = max(in);
mean_val = mean(in);
end

[Sanley Guerrier]

I appriciate it. That helps a lot!