h5read - howto read values in hexadecimal

Question

Beder 2016-11-20

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313155-h5read-howto-read-values-in-hexadecimal

评论： Beder 2016-12-6

Dear all, currently I'm trying to write h5-files containing singles into a sql-database expecting floats (single).

Matlab reads the data of the h5 files into singles. Due to the use of sprintf and a matrix containing singles and doubles I unfortunately need to change them to double. Otherwise the values of the generated sprintf gets weird.

So I'm searching for a way howto read the h5 files as hexadecimal, therefore not altering the values and transferring them in hexadecimal to my sql-database.

I would be very pleased to get help - since I did not find anything on google.

This is the code I'm using:

conn =database.ODBCConnection('FirstTryLocal','user','Password');
for mint=1:10;
maxt=mint;
countt=maxt-mint+1;
for minlat=1:36:360-35;
maxlat=minlat+35
countlat=maxlat-minlat+1;
minlon=1;
maxlon=540;
countlon=maxlon-minlon+1;
n=datenum('20120101000000','yyyymmddHHMMSS');
cutstart=[minlat minlon mint];
cutlength=[36 maxlon maxt-mint+1];
evap= double(h5read('path','/data',cutstart,cutlength));
v50= double(h5read('path','/data',cutstart,cutlength));
t=1:countt;
lat=minlat:maxlat;
lon = minlon:maxlon;
datum=round(str2num(datestr(n+(mint+t-2)./24,'yymmddHH')));
a = repmat(datum', [countlon*countlat 1]);
b = repmat(lat,[countlon countt]);
c = repmat(lon',[countt countlat]);
d = permute(evap,[2 1 3]);
m = permute(v50,[2 1 3]);
str5=sprintf('\r\n (%d%03d%03d, %d, %i, %i, %d, %d), ', [a(:)'; b(:)'; c(:)'; a(:)'; b(:)'; c(:)'; m(:)']);
%str5=sprintf('\r\n (%d), ', [a(:)']);
sqlquery = strcat('INSERT INTO datanew (ID, datum, lat, lon, evap, v50) VALUES ',str5);
insertQuery = [sqlquery(1:end-1),';'];
response=exec(conn,insertQuery);
if isempty(response.Message)
else
    disp(strcat('Error during import of time ',num2str(datum(1)),' and ',num2str(datum(end)),', ',num2str(minlat),', ',num2str(maxlat),', ',num2str(minlon),', ',num2str(maxlon)));
    disp(response.Message)
    if strcmp(response.Message,'ODBC Driver Error: [ma-1.0.6][10.1.19-MariaDB]MySQL server has gone away')
    disp('This Error appears due to the size of the SQL-Query. Please reduce the amout of data transfered. E.g. 360x540x1')
    end
    pause
end
end
end
toc
close(conn)

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Jan 2016-11-20

What does "Due to the use of sprintf and a matrix containing singles and doubles" mean? Matrices cannot contain values of different type.

Beder 2016-12-6

Hi, sorry for the late reply. Didn't see your answer.

When using sprintf with one matrix being double, all the others need to be double as well. The Matrix with the datenum is double - this is why I need to convert all my other values to double as well.

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Answer 1

Sid Jhaveri 2016-12-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313155-h5read-howto-read-values-in-hexadecimal#answer_246044

1) I believe that the HDF5 file that you are reading contains singles and you would like to convert it into hexadecimal values. You can do so by using “ num2hex ” function. Thus, instead of the converting your singles into doubles, convert it into hexadecimal values.

For example, instead of using,

evap= double(h5read('path','/data',cutstart,cutlength));

use,

evap= num2hex(h5read('path','/data',cutstart,cutlength));

2) You can also try to convert the double precision values into single precision values by using “ single ” function. This way, all the numeric values in your code will be single precision.

I hope is helps.

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Beder 2016-12-6

Thank you very much for the information. I didn't know about num2hex. And I didn't know, that it does not somehow alter the values of the single-datatype. It helps a lot. Thank you

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