for loop with structure+matlab - matlab

Question

I have a structure named sacfile which has data for various stations within it (sta1-sta6). The sacfile is further borken up into day increments (sacfile.day, per station), and further into hourly increments for each day (sacfile.day.hour). I would like to loop through each day and subsequently through each hour for each station comparison (i.e., day 032 loop through sta1 hr 1 compared to sta2 hr 1, sta3 hr 1, sta4 hr1, sta5 hr1, sta6 hr 1, and so on and so forth through all the hours of that day, then move onto the next day, etc. You get the point. The stations are defined in sacfile.sta. Does anyone have any suggestion on how I can do this simply?
*I only want to loop through the same day and hour for the stations, then move onto the subsequent day and hour. I don't want to cross compare different days and hours. This is important for the loop.
I tried the following:
for i = 1:length(sacfile)
for j = 1:length(sacfile(i,1).day)
for h = 1:length(sacfile(i,1).day.hour)
but that seems to loop through every hour point. Will this work, how can I be assured it's looping through the correct days, i.e., that day 1 for sta1 is the same day1 for sta2.
Here's an example of one of the structures:
name: '2013.032.00.00.00.0000.TA.POKR..BHE.sac'
date: '31-Mar-2014 12:25:33'
bytes: 11949036
isdir: 0
datenum: 7.3569e+05
net: 'TA'
sta: 'POKR'
loc: ''
comp: 'BHE'
day: [1x1 struct]
data: [2987101x1 double]
time: [1x2987101 double]
header: [1x1 struct]
The only relevent ones are net, sta, loc, comp, day and data. The net, sta, loc, comp are the key identifying fields for the file. The name is the name of the file. Day has the data broken up into hours within it. Make sense?

Answer 1

If I understood your problem well, the functions extractfield() and fieldnames() should help.
fields = fieldnames(sacfile);
for i = 1:numel(fields)
b = extractfield(sacfile.(fields{i}).day, 'day3');
c(i) = extractfield(b{1}.hour, 'hour_x');
end
The function extractfield() returns 1x1 cell containing a structure instead of the structure itself. That is why I do b{1}