I want to do something like
scatter(timesRefined, upProb)
where timesRefined is a cell array in which each entry is a string corresponding to a time moment, such as 8:32:21.122 and upProb is simply a vector of numbers with same length as cell array. What is the most convenient way to do this?
You can convert your timesRefined cell to a numeric representation of date with datenum
>> timesRefined = {'8:32:21.122','9:30:54.123'};
>> datenum(timesRefined)
ans =
734869.355800023
734869.396459757
The resulting number expresses a date as days from the epoch. Since you are not concerned with days, just time, and provided your observations are contained within one day, you can simply take the fractional part of the datenum output:
>> datestr(mod(datenum(timesRefined),1))
ans =
8:32 AM
9:30 AM
and do scater(mod(datenum(timesRefined),1),upProb)
EDIT:
As pointed out by Pursuit, you can use the result of datenum directly as your x values and use datetick('x','HH:MM:SS.FFF')
strsplit from the Matlab file exchange should help. If all values are numeric, you'll get a matrix back.
timestr = '8:32:21.122';
timenum = strsplit(timestr,':');
convmat = [60*60; 60; 1];
time_in_seconds = sum(timenum .* convmat);
Related
MATLAB R2015b
I have a table containing a date string and a time string in various formats in two columns for each row:
11.01.2016 | 00:00:00 | data
10/19/16 | 05:29:00 | data
12.02.16 | 06:40 | data
I want to convert this two columns to one column with a common format:
31.12.2017 14:00:00
My current solution uses a loop over each row and combines the columns as strings, checks for the various formats to use datetime with an appropriate format string and then uses datestr with the desired format string. Datetime was not able to automatically determine the format of the input string.
As you can imagine, this is horribly slow for large tables (approx. 50000 rows).
Is there any faster solution?
Thanks in advance.
I gave a try to vectorize the code. The trick is to
convert tables > cell > char-array, then
manipulate char strings, then
convert back from char-array > cell > table
Also, there is an important bit to pad all cells having shorter lenths with 'null' character in a vectorized way. Without this, it will not be possible to convert from cell > char-array. Here is the code.
clc
clear all
%% create Table T
d={'11.01.2016';
'10/19/16';
'12.02.16'};
t={'00:00:00';
'05:29:00';
'06:40'};
dat=[123;
456;
789];
T = table(d,t,dat);
%% deal with dates in Table T
% separate date column and convert to cell
dd = table2cell(T(:,1));
% equalize the lengths of all elements of cell
% by padding 'null' in end of shorter dates
nmax=max(cellfun(#numel,dd));
func = #(x) [x,zeros(1,nmax-numel(x))];
temp1 = cellfun(func,dd,'UniformOutput',false);
% convert to array for vectorized manipulation of char strings
ddd=cell2mat(temp1);
% replace the separators in 3rd and 6th location with '.' (period)
ddd(:,[3 6]) = repmat(['.' '.'], length(dd),1);
% find indexes of shorter dates
short_year_idx = find(uint16(ddd(:,nmax)) == 0);
% find the year value for those short_year cases
yy = ddd(short_year_idx,[7 8]);
% replace null chars with '20XX' string in desirted place
ddd(short_year_idx,7:nmax) = ...
[repmat('20',size(short_year_idx,1),1) yy];
% convert char array back to cell and replace in table
dddd = mat2cell(ddd,ones(1,size(d,1)),nmax);
T(:,1) = table(dddd);
%% deal with times in Table T
% separate time column and convert to cell
tt = table2cell(T(:,2));
% equalize the lengths of all elements of cell
% by padding 'null' in end of shorter times
nmax=max(cellfun(#numel,tt));
func = #(x) [x,zeros(1,nmax-numel(x))];
temp1 = cellfun(func,tt,'UniformOutput',false);
% convert to array for vectorized manipulation of char strings
ttt=cell2mat(temp1);
% find indexes of shorter times (assuming only ':00' in end is missing
short_time_idx = find(uint16(ttt(:,nmax)) == 0);% dirty hack, as null=0 in ascii
% replace null chars with ':00' string
ttt(short_time_idx,[6 7 8]) = repmat(':00',size(short_time_idx,1),1);
% convert char array back to cell and replace in table
tttt = mat2cell(ttt,ones(1,size(t,1)),nmax);
T(:,2) = table(tttt);
If you call the two columns cell arrays c1 and c2, then something like this should work:
c = detestr(datenum(strcat(c1,{' '},c2)), 'dd.mm.yyyy HH:MM:SS')
Then you would need to drop the old columns and put this one c in their place. On the inside, datenum must be doing something similar to what you're doing, however, so I'm not sure if this will be faster. I suspect that it is because (we can hope) the standard functions are optimized.
If your table isn't representing those as cell arrays, then you may need to do a pre-processing step to form the cell arrays for strcat.
I ve got an ascii file and im trying to import it to matlab in order to make some plots. Is there any way of importing those data, even tho they contain , (comma) rather than . (dot)?
00:00:00,000;-2,14;
00:00:00,001;-1,80;
Well the first column which I want to create is referred to the time and its corresponding to 00:00:00,001; 00:00:00,002; etc.
The second column should be the amplitude of the sample i.e. -2,14; -1,80 etc.
Yup. First use importdata so that you can read each row of your text file as a cell in a cell array. After, to allow for the processing of your times to be performed in MATLAB, you'll need to replace each , character with a .. This will allow you to use MATLAB's commands for date and time processing. Specifically, use regular expressions to help you do this. Regular expressions help you find patterns in strings. We can use these patterns to help extract out the data you need. Use regexprep to replace all , characters with a ..
For the purposes of this answer, the example data that I'm going to be using is:
00:00:00,000;-2,14;
00:00:00,001;-1,80;
00:00:00,002;-0,80;
00:00:00,003;2,40;
00:00:00,004;3,78;
Therefore, assuming that your data is stored in a text file called data.txt, do:
%// Load in each row as a cell array
A = importdata('data.txt');
%// Each row has , replaced with .
Arep = regexprep(A, ',', '\.');
Now, what we can do is split up all of the quantities by using ; as the delimiter. We can use regexp to help us split up the quantities. We can further decompose the data by:
Arep_decomp = regexp(Arep, '[^;]+', 'match');
The first parameter is the cell array that contains each of our rows in the text file (with the commas converted to periods). The second parameter is a pattern that specifies what exactly you're trying to look for in each string in the cell array. [^;]+ means that you want to find all strings that consist of a bunch of characters excluding until we hit a semi-colon. Once we hit the semi-colon, we stop. 'match' means that you want to retrieve the actual strings which will be stored as cell arrays.
The result after the above line's execution gives:
Arep_decomp{1}{1} =
00:00:00.000
Arep_decomp{1}{2} =
-2.14
Arep_decomp{2}{1} =
00:00:00.001
Arep_decomp{2}{2} =
-1.80
Arep_decomp{3}{1} =
00:00:00.002
Arep_decomp{3}{2} =
-0.80
Arep_decomp{4}{1} =
00:00:00.003
Arep_decomp{4}{2} =
2.40
Arep_decomp{5}{1} =
00:00:00.004
Arep_decomp{5}{2} =
3.78
You can see that the output cell array, Arep_decomp is a 5 element cell array, where each cell is a nested 2 element cell array, where the first element is the time, and the second element is the magnitude. Note that these are all strings.
What you can do now is create two numeric arrays that will convert these quantities into numeric representations. Specifically, the time format that you have looks like the form:
HH:MM:SS.FFF
H is for hours, M is for minutes, S is for seconds and F is for microseconds. Use datenum to allow you to convert these time representations into actual date numbers. You would do this so that you can plot these on a graph, but then you perhaps want to display these times on the plot as well. That can easily be done by manipulating some plot functions. Nevertheless, use cellfun so that we can extract out the time strings as a separate array so we can use this for plotting later, and also use this to convert the time strings into date numbers via datenum, and convert the magnitude numbers into actual numbers.
Therefore:
datestr = cellfun(#(x) x{1}, Arep_decomp, 'uni', 0);
datenums = cellfun(#(x) datenum(x, 'HH:MM:SS.FFF'), datestr);
mags = cellfun(#(x) str2double(x{2}), Arep_decomp);
The first line of code extracts out each of the time strings as a single cell array - the uni=0 flag is important to do this. Next, we convert each time string into a date number, and we convert the magnitude strings into physical numbers by str2double.
Now, all you have to do is plot the data. That can be done by:
plot(datenums, mags);
set(gca, 'XTick', datenums);
set(gca, 'XTickLabel', datestr);
The above code plots the data where the date numbers are on the horizontal axis, the magnitude numbers are on the vertical axis, but we will probably want to rename the horizontal axis to be those time strings that you wanted. Therefore, we use to calls to set to ensure that the only ticks that are visible are from the date numbers themselves, and we relabel the date numbers so that they are the string representations of the times themselves.
Once we run the above code, we get:
Because the time step in between times is so small, it may clutter the horizontal axis as the labels are long, yet the interval is short. Therefore, you may consider only displaying times at a certain interval and you can do that by doing something like:
step_size = 5;
plot(datenums, mags);
set(gca, 'XTick', datenums(1:step_size:end));
set(gca, 'XTickLabel', datestr(1:step_size:end));
step_size controls how many ticks and labels appear in succession. Obviously, you need to make sure that step_size is smaller than the total number of points in your data.
For your copying and pasting pleasure, this is what the full code I wrote looks like:
%// Load in each row as a cell array
A = importdata('data.txt');
%// Each row has , replaced with .
Arep = regexprep(A, ',', '\.');
Arep_decomp = regexp(Arep, '[^;]+', 'match');
datestr = cellfun(#(x) x{1}, Arep_decomp, 'uni', 0);
datenums = cellfun(#(x) datenum(x, 'HH:MM:SS.FFF'), datestr);
mags = cellfun(#(x) str2double(x{2}), Arep_decomp);
step_size = 1;
%step_size = 5;
plot(datenums, mags);
set(gca, 'XTick', datenums(1:step_size:end));
set(gca, 'XTickLabel', datestr(1:step_size:end));
I have a time series xlsx data which has columns like the following one. I would like to get the row data that are in between 8:00:00 AM to 10:00:00 AM for my analysis. Can any one help me out?
Add Velocity Time
0.128835374 10.34912454 8:44:23 AM
0.20423977 8.078739988 8:47:01 AM
0.110629502 13.4081172 9:19:46 AM
0.088979639 5.057336749 9:24:02 AM
0.128835374 10.60785265 10:21:29 AM
0.20423977 9.46599837 10:23:06 AM
[num, txt] = xlsread('Consective_result.xlsx');
T = num(:,3);
TimeVector = datevec(T)
You almost have it right. Use the third column of your txt cell array, and skip over the first row so you don't get the time header. I'm going to assume that your times are entered in as text. Once you do this, just use datenum and determine those times that are later than 8:00 AM and less than 10:00 AM. datenum can conveniently take in a cell array of strings, and it will output a numeric vector where each time string in your cell array is converted into its corresponding numerical representation.
Once you find those rows, you can filter out the rows in each of num and txt using what we just talked about before you continue. Therefore:
[num, txt] = xlsread('Consective_result.xlsx');
times = txt(2:end,3); %// Get the 3rd column, skip 1st row
time_nums = datenum(times); %// Get the numerical representation of the times
%// Figure out those rows that are between 8:00 AM and 10:00 AM
times_to_choose = time_nums >= datenum('08:00:00AM') & time_nums <= datenum('10:00:00AM');
%// Remove those rows then continue
num(1 + times_to_choose) = [];
txt(1 + times_to_choose) = [];
Take special care that I added a 1 to the indices because we omitted the time header in your spreadsheet. Now, num and txt should only contain those times that are between 8:00 AM and 10:00 AM.
I'm importing large datasets into Matlab from different Excel files. I use [~,~,raw] = xlsread('myfile.xlsx') to obtain a raw input into a single Matlab cell.
One column consists of interest rates, and the entries are imported as either CHAR (if they're decimal numbers) or DOUBLE (if they're rounded to integers).
Now, I want to slice out that column and get a numerical vector, which Matlab doesn't like. If i use str2num, all the CHAR entries are converted into DOUBLE, but the DOUBLES becomes NaN. Is there a function/solution to take into account that some entries are already DOUBLE?
You can probably work this into your existing code rather than create a whole new function but this should work for you. The functions not vectorized though but since it a cell vector I don't think that's an issue
function number = str2numThatHandelsNumericInputs(obj)
if isnumeric(obj)
number = obj;
else
number = str2num(obj);
end
end
Or as Eitan points out a better function:
function num = str2numThatHandelsNumericInputs(num)
if ischar(num)
num = str2num(num);
end
end
I think I didn't quite understand your question, because I understood you have something like this:
raw = {...
'1.2345' , NaN
3 , inf
4 , #cos
'567.1232' , { struct }
};
In which case you could just use str2double:
>> inds = cellfun('isclass', raw(:,1), 'char'); % indices to non-numeric data
>> raw(inds,1) = num2cell(str2double(raw(inds,1))); % convert in-place
>> [raw{:,1}].' % extract numeric array
ans =
1.2345
3.0000
4.0000
567.1232
But is this what you mean?
I have strings of the format '15:10:21' for time, and I also know the date, which is in the format 2011-08-05.
What's the best way to obtain matlab time (in days since 1900) out of this data?
Use datenum:
>> num = datenum('2011-08-05 15:10:21')
num =
7.3472e+05
>> datestr(num)
ans =
05-Aug-2011 15:10:21
The "matlab time" is actually days since the 0th of January, in the year 0:
>> datestr(0)
ans =
00-Jan-0000