I'm currently working on a small project on handling time difference on MATLAB. I have two input files; Time_in and Time_out. The two files contain arrays of time in the format e.g 2315 (GMT - Hours and Minute)
I've read both Time_in' and 'Time_out on MATLAB but I don't know how to perform the subtraction. Also, I want the corresponding answers to be in minutes domain only e.g (2hrs 30mins = 150minutes)
this is one of several possible solutions:
First, you should convert your time strings to a MATLAB serial date number. If you've done this, you can do your calculation as you want:
% input time as string
time_in = '2115';
time_out = '2345';
% read the input time as datenum
dTime_in = datenum(time_in,'HHMM');
dTime_out = datenum(time_out,'HHMM');
% subtract to get the time difference
timeDiff = abs(dTime_out - dTime_in);
% Get the minutes of the time difference
timeout = timeDiff * 24 * 60;
Furthermore, to calculate the time differences correctly you also should put some information about the date in your time vector, in order to calculate the correct time around midnight.
If you need further information about the function datenum you should read the following part of the MATLAB documentation:
https://de.mathworks.com/help/matlab/ref/datenum.html
Any questions?
In a recent version of MATLAB, you could use textscan together with datetime and duration data types to do this.
% read the first file
fh1 = fopen('Time_in');
d1 = textscan(fh1, '%{HHmm}D');
fclose(fh1);
fh2 = fopen('Time_out');
d2 = textscan(fh2, '%{HHmm}D');
fclose(fh2);
Note the format specifier '%{HHmm}D' tells MATLAB to read the 4-digit string into a datetime array.
d1 and d2 are now cell arrays where the only element is a datetime vector. You can subtract these, and then use the minutes function to find the number of minutes.
result = minutes(d2{1} - d1{1})
Related
I am reading system time(Register: TM11), and I want to get minute data from system time.
system time is in this data format = 3 bytes:{Hour}{Minute}{Second}
I am not sure, how to extract "minute" data, using array format, C code as below.
In my C code below, i use read_register function for reading system time, and use pointer (byte*)&systime[1]) to extract "minute". -not sure this is correct way to do so.
let's say, time now is 07:48:29 AM then, TM11 will show 07,48,29
I want to extract "48", which is minute, from TM11.
time interval: 15 minute.
Time Passed = 48 % 15 = 3 minute.
Putting this calculation in the C,
byte systime[2];
//declare "systime" variable as 3 byte array and to store TM11 //
byte time_interval = 15; //time interval is 15 minute
read_register (TM11,(byte*)&systime[1]);
//let's say read data value of TM11 is, 07:48:29 AM
//"read_register"function is to read the value of TM11 register
//(byte*)&systime[1] =try to point "minute" in TM11 register, systime[1]=48
//I am not sure whether hour will store in systime[0], minute will store in systime[1],//
elaps_time = systime[1] % time_interval;
//elapsed time calculation = 48 % 15 = 3
I have an array that contains multiple dates in the format yyyymmdd, stored as a 50x1 double. I am trying to pull out the year,month, and day so I can use datenum to assign each date a serial number.
Indexing an individual date, converting the using str2num, then indexing and pulling the appropriate values works fine, but when I try to loop through the list of dates it doesn't work- only variations of the number 2 are returned.
dates = [20180910; 20180920; 20181012; 20181027; 20181103; 20181130; 20181225];
% version1
datesnums=num2str(dates); % dates is a list of dates stored as
integers
for i=1:length(datesnums)
pullyy=str2num(datesnums(1:4));
pullmm=str2num(datesnums(5:6));
pulldd=str2num(datesnums(7:8));
end
As well as
%version2
datesnums=num2str(dates,'%d')
for i = 1:length(datesnums)
dd=datenum(str2num(datesnums(i(1:4))),str2num(datesnums(i(5:6))),
str2num(datesnums(i(7:8))));
end
I'm trying to generate a new array that is just the serial numbers of the input dates. In the examples shown, I am only getting single integer values, which I know is because the loop is incorrect and I get errors that say "Index exceeds the number of array elements (1)." for version 1. When I've gotten it to successfully loop through everything, the outputs are just '2222','22,'22' for every single date which is incorrect. What am I doing wrong? Do I need to incorporate a cell array?
To get all the years, month, and days in a loop:
datesnums=num2str(dates);
for i=1:size(datesnums, 1)
pullyy(i) = str2num(datesnums(i,1:4));
pullmm(i) = str2num(datesnums(i,5:6));
pulldd(i) = str2num(datesnums(i,7:8));
end
Actually, you can do this without a loop:
pullyy = str2num(datesnums(:,1:4));
pullmm = str2num(datesnums(:,5:6));
pulldd = str2num(datesnums(:,7:8));
Explanation:
If for example the dates vector is a [6x1] array:
dates =[...
20190901
20170124
20191215
20130609
20141104
20190328];
Than datesnums=num2str(dates); creates a char matrix of size [6x8] where each row corresponds to one element in dates:
datesnums =
6×8 char array
'20190901'
'20170124'
'20191215'
'20160609'
'20191104'
'20190328'
So in the loop you need to refer to the row index for each date and and the column indices to extract the years, month, and days.
The easiest solution I can think of is:
SN = datenum(num2str(dates),'yyyymmdd')
You only have to specify the date format which is 'yyyymmdd'
I have a cell array called BodyData in MATLAB that has around 139 columns and 3500 odd rows of skeletal tracking data.
I need to extract all rows between two string values (these are timestamps when an event happened) that I have
e.g.
BodyData{}=
Column 1 2 3
'10:15:15.332' 'BASE05' ...
...
'10:17:33:230' 'BASE05' ...
The two timestamps should match a value in the array but might also be within a few ms of those in the array e.g.
TimeStamp1 = '10:15:15.560'
TimeStamp2 = '10:17:33.233'
I have several questions!
How can I return an array for all the data between the two string values plus or minus a small threshold of say .100ms?
Also can I also add another condition to say that all str values in column2 must also be the same, otherwise ignore? For example, only return the timestamps between A and B only if 'BASE02'
Many thanks,
The best approach to the first part of your problem is probably to change from strings to numeric date values. In Matlab this can be done quite painlessly with datenum.
For the second part you can just use logical indexing... this is were you put a condition (i.e. that second columns is BASE02) within the indexing expression.
A self-contained example:
% some example data:
BodyData = {'10:15:15.332', 'BASE05', 'foo';...
'10:15:16.332', 'BASE02', 'bar';...
'10:15:17.332', 'BASE05', 'foo';...
'10:15:18.332', 'BASE02', 'foo';...
'10:15:19.332', 'BASE05', 'bar'};
% create column vector of numeric times, and define start/end times
dateValues = datenum(BodyData(:, 1), 'HH:MM:SS.FFF');
startTime = datenum('10:15:16.100', 'HH:MM:SS.FFF');
endTime = datenum('10:15:18.500', 'HH:MM:SS.FFF');
% select data in range, and where second column is 'BASE02'
BodyData(dateValues > startTime & dateValues < endTime & strcmp(BodyData(:, 2), 'BASE02'), :)
Returns:
ans =
'10:15:16.332' 'BASE02' 'bar'
'10:15:18.332' 'BASE02' 'foo'
References: datenum manual page, matlab help page on logical indexing.
I am in WinCE7 and to get the current time, I am using GetLocalTime(&systemTime);. This function gives the value of current time. Now if the milliseconds is 81, it displays it as 81 due to which the error occurs when I subtract two time values. For ex: time1 : 12:34:13:851 & time2: 12:34:14:81. Now I need to subtract seconds and milliseconds. So using sprintf, I am extracting seconds and milliseconds and putting them in time1 & time2 :
sprintf(time1,"%d.%d",systemTime.wSeconds,systemTime.wMilliseconds)
sprintf(time2,"%d.%d",systemTime.wSeconds,systemTime.wMilliseconds)
I am converting time1 & time2 into float using atof.Now time1 is 13.851 and time2 is 14.81. The milliseconds of time2 is actually 081 but it displays 81 so while subtracting it consider it as 810 which gives wrong values.
time2--> 14.810 14.081
time1--> 13.851 13.851
-------- ---------
result 0.959(wrong) 0.23(correct)
So to remove this error I thought of counting the digits of milliseconds and if it is 2 then add 0 at starting. So I did:
double digits = (floor (log10 (abs (milliseconds))) + 1); //calculate digits
if(digits == 2) //if milliseconds contains 2 digits, we need to add 0 at starting
{
sprintf(newMS,"0%d",milliseconds); //adding 0 to milliseconds
finalMilliseconds = atoi(newMS); //newMS is in char so converting it into integer and storing the value in finalMilliseconds
}
The problem occurs here. Lets say milliseconds = 18, so newMS = 018 but finalMilliseconds is again 18.
Please suggest any other way of conversion or any other way of adding 0 at starting
According to the documentation of SYSTEMTIME from MSDN:
It is not recommended that you add and subtract values from the
SYSTEMTIME structure to obtain relative times. Instead, you should
Convert the SYSTEMTIME structure to a FILETIME structure.
Copy the resulting FILETIME structure to a ULARGE_INTEGER structure.
Use normal 64-bit arithmetic on the ULARGE_INTEGER value.
The example here will give you some idea on how to get started.
It seems to me the simplest solution is to borrow what you need.
You already have integers. If you're subtracting two systemTime values, t2 from t1, say,
if( t1.wMilliseconds < t2.wMilliseconds ) {
t1.wMilliseconds += 1000;
t1.wSeconds--;
}
Or, just perform the subtraction. If the result's wMlliseconds is negative, adjust as above.
Take care to ensure t1 > t2, though. You don't want -1.25 = 0.0 - 0.75.
Instead of putzing with strings, if you want a float, make one:
double time1 = t1.wSeconds + 0.001 * t1.wMilliseconds;
C does the conversion for you. It's faster, more direct, and less error-prone than going through strings.
Another way of dealing with these marvels of lost leading or trailing zeroes (found in time and longlat), is to right pad the string with say four zeroes .i.e your newMS+"0000", and take the leftmost four characters.
You then have a number (as text) ranging from "0000" to "9990".
Put a "1" in front of it, then you can easily and unambiguously convert to an integer between 10000 and 19990.
Then you can add and subtract as you like.
Clumsy? Yes indeed :) But I have had to do weird tricks like this when GPS longitude readings go from 11.59(funny numbers) to 12.00
I want to accept (say)3 time elements (for example 8:30, 8:20 & 8:00) from user and store it in an array using 'datenum'. How can i achieve that? Please help.
Assuming that you just want to prompt the user given the current day and year and you only want the current time (hours and minutes - seconds is 0), you can do the following:
dateNumArray = []; %// Store datenums here
%// Enter a blank line to quit this loop
while true
timestr = input('Enter a time: ', 's');
if (isempty(timestr))
break;
end
%// Split the string up at the ':'
%//splitStr = strsplit(timestr, ':'); %// For MATLAB R2012 and up
splitStr = regexp(timestr, ':', 'split');
%// Read in the current date as a vector
%// Format of: [Year, Month, Day, Hour, Minute, Second]
timeRead = clock;
%// Replace hours and minutes with user prompt
%// Zero the seconds
timeRead(4:6) = [str2num(splitStr{1}) str2num(splitStr{2}) 0];
%// Convert to datenum format
dateNumArray = [dateNumArray datenum(timeRead)];
end
What the above code does is that we will keep looping for user input, where the time is expected to be in HH:MM format. Note that I did not perform error checking, so it is expected that HH is between 0-23 while MM is between 0-59. You keep putting in numbers by pushing in ENTER or RETURN for each entry. It parses this as a string, splits the string up at the : character, and converts each part before and after the : character into a number. We then get the current time when each hour and minute was recorded using the clock command. This is in a 6 element vector where the year, the month, the day, the hour, the minute and the second are recorded. We simply replace the hour and minute with what we read in from the user, and zero the seconds. We finally use this vector and append this to a dateNumArray variable where each time the user writes in a time, we will append a datenum number into this array.
When you call this, here is an example scenario:
Enter a time: 8:30
Enter a time: 8:45
Enter a time: 8:00
Enter a time:
Here's the example output from above:
format bank %// Show whole numbers and little precision
dateNumArray
format %// Reset format
dateNumArray =
735778.35 735778.36 735778.33