Regarding plotting using .csv file in QWT

Hi Uwe,

I am using qwt library to draw a graph of Time Vs Temperature in my project
where the data is fed to curve by reading from a csv file as a text.

However I am able to read the values of the csv file when I qdebug in my code,
but am not able to draw those on to the plot.

The QwtPlotCurve class takes parameters only in double and converting the string
info from .csv file to double and feeding it by still it is not drawing those
values.The csv file contains Time and temperature and this data set/pair comes
for every 5 secs.
setRawSamples() function i am using.

Do you have any examples which read csv file and plot accordingly?

Does qwt supports Embedded Linux as well? also does it support touch events such
as thumb and fore finger zooming, panning right now they are happening from
classes QwtPlotPanner and QwtPlotMagnifier through mouse events.

These are versions that I am using currently
QtCreator: 2.0.1
Qt Version : 4.7
QWT Version: 6.0.1

Awating your reply.

Thanks in advance.

Hello Ravikiran,

Many of the people who subscribe to the Qwt mailing list also watch this forum.

You didn't like the answer you got in the mailing list, so you thought reposting the exact same question here would get you a different answer? That is a little bit insulting to people who are polite enough to give you an answer, don't you think?

David

Hi David,

Its not so.I am not insulting any one. I did not find QWT mailing list that much friendly and was also not able get clearly see responses to my questions as I have registered to it recently.
The day I posted my question on QWT mailing list , I also posted in QtCentre as well.So no question of insulting, as I was even not knowing that many people are registered with QWT mailiing list.

BR,
Ravikiran

Back to your CSV files I recommend to organize your question like you would organize your code:

• How to load a CSV files into a QPolygonF
• How to display a QPolygonF on a QwtPlot

The first question is completely unrelated to Qwt and I'm pretty sure that you can solve this problem easily. If not ask in the newbie section of this forum or google for "csv file qt".

The second question is simply:

Code:

---

curve->setSamples( polygon );

---

Uwe

Quote:

---

Its not so.I am not insulting any one. I did not find QWT mailing list that much friendly and was also not able get clearly see responses to my questions as I have registered to it recently.
The day I posted my question on QWT mailing list , I also posted in QtCentre as well.So no question of insulting, as I was even not knowing that many people are registered with QWT mailiing list.

---

OK, my mistake for jumping to a conclusion. I apologize. In case you did not get the answer I posted to the Qwt mailing list, here it is:

> Do you have any examples which read csv file and plot accordingly?

Posting a question with no example code means that we have to guess what
you might be doing wrong. We can make up answers all day long and never
know if we've told you the real answer. It is like asking "How long is
a piece of string?"

Reading data points from *anywhere* and plotting them using QwtPlot are
completely unrelated problems.

- Have you looked at the arrays of data you are sending to QwtPlot to
see if they actually contain the numbers you see in your CSV file? How
do you know the reading is successful? How do you know the parsing from
string to number is successful?

- If the arrays *do* contain the numbers you expect, how do you allocate
these arrays? The setRawData() method *requires* that the array
pointers be valid for the lifetime of the QwtPlotCurve that is using
them. If your arrays go out of scope before the curve does, then the
curve is trying to use invalid pointers to draw.

- Did you set the axis ranges to match the data ranges? If the data is
outside the range of the plot, then the curve might be drawn, but
nothing is visible because it is outside the axes.

- Did you set the curve style to be "Lines" and the pen to be something
visible? If the style is set to "NoCurve", then it will be invisible.

> also does it support touch events

David

Hi Uwe,

Thanks for the earlier answer.

My other concern is does Qwt support embedded Linux? because my project is very much based on Qt Embedded Linux 4.7 running on Free scale's IMX 233 H/W board with ARM 11 Compiler which also need to support plot zoom and panning.

Is it straight forward process or do we have do put some effort?Please revert back to this.

BR,
Aster

Quote:

---

Originally Posted by Aster036

My other concern is does Qwt support embedded Linux?

---

I never heard of a platform. where someone was running Qt and Qwt didn't work - Qwt depends on Qt and the C-library only, no other libraries ( boost, STL ) are used.

I know many applications running QWS on embedded Linux ( see youtube ) and wrote large applications in this environment myself - but of course you always have to check your environment yourself.

Uwe

Hi ,

When installing qwt-6.0.0-rc5 on Ubuntu 10.04 I am getting below error :

1) qmake qwt.pro works fine
2) when ran command "make" it is giving below error:

/Desktop/qwt-6.0.0-rc5$ make
cd src && make -f Makefile
make[1]: Entering directory `/home/ravi/Desktop/qwt-6.0.0-rc5/src'
compiling qwt_interval.cpp
In file included from qwt_interval.cpp:10:
qwt_interval.h:24: error: variable ‘QWT_EXPORT QwtInterval’ has initializer but incomplete type
qwt_interval.h:24: warning: extended initializer lists only available with -std=c++0x or -std=gnu++0x
qwt_interval.h:26: error: expected primary-expression before ‘public’
qwt_interval.h:26: error: expected ‘}’ before ‘public’
qwt_interval.h:26: error: expected ‘,’ or ‘;’ before ‘public’
qwt_interval.h:51: error: expected constructor, destructor, or type conversion before ‘;’ token
qwt_interval.h:53: error: ‘IncludeBorders’ was not declared in this scope
qwt_interval.h:53: error: expected constructor, destructor, or type conversion before ‘;’ token
qwt_interval.h:56: error: ‘IncludeBorders’ was not declared in this scope
qwt_interval.h:58: error: ‘QwtInterval’ does not name a type
qwt_interval.h:59: error: ‘QwtInterval’ does not name a type
qwt_interval.h:60: error: ‘QwtInterval’ does not name a type
qwt_interval.h:62: error: ISO C++ forbids declaration of ‘QwtInterval’ with no type
qwt_interval.h:62: error: expected ‘,’ or ‘...’ before ‘&’ token
qwt_interval.h:62: error: non-member function ‘bool operator==(int)’ cannot have cv-qualifier
qwt_interval.h:62: error: ‘bool operator==(int)’ must have an argument of class or enumerated type
qwt_interval.h:63: error: ISO C++ forbids declaration of ‘QwtInterval’ with no type
qwt_interval.h:63: error: expected ‘,’ or ‘...’ before ‘&’ token
qwt_interval.h:63: error: non-member function ‘bool operator!=(int)’ cannot have cv-qualifier
qwt_interval.h:63: error: ‘bool operator!=(int)’ must have an argument of class or enumerated type
qwt_interval.h:66: error: non-member function ‘int borderFlags()’ cannot have cv-qualifier
qwt_interval.h:68: error: non-member function ‘double minValue()’ cannot have cv-qualifier
qwt_interval.h:69: error: non-member function ‘double maxValue()’ cannot have cv-qualifier
qwt_interval.h:71: error: non-member function ‘double width()’ cannot have cv-qualifier
qwt_interval.h:76: error: non-member function ‘bool contains(double)’ cannot have cv-qualifier
qwt_interval.h:78: error: ISO C++ forbids declaration of ‘QwtInterval’ with no type
qwt_interval.h:78: error: expected ‘,’ or ‘...’ before ‘&’ token
qwt_interval.h:78: error: non-member function ‘bool intersects(int)’ cannot have cv-qualifier
qwt_interval.h:79: error: ‘QwtInterval’ does not name a type
qwt_interval.h:80: error: ‘QwtInterval’ does not name a type
qwt_interval.h:82: error: expected constructor, destructor, or type conversion before ‘operator’
qwt_interval.h:83: error: expected constructor, destructor, or type conversion before ‘operator’
qwt_interval.h:85: error: expected constructor, destructor, or type conversion before ‘&’ token
qwt_interval.h:86: error: expected constructor, destructor, or type conversion before ‘&’ token
qwt_interval.h:88: error: ‘QwtInterval’ does not name a type
qwt_interval.h:89: error: expected constructor, destructor, or type conversion before ‘operator’
qwt_interval.h:90: error: expected constructor, destructor, or type conversion before ‘&’ token
qwt_interval.h:92: error: non-member function ‘bool isValid()’ cannot have cv-qualifier
qwt_interval.h:93: error: non-member function ‘bool isNull()’ cannot have cv-qualifier
qwt_interval.h:96: error: ‘QwtInterval’ does not name a type
qwt_interval.h:98: error: expected unqualified-id before ‘private’
qwt_interval.h:102: error: expected declaration before ‘}’ token
make[1]: *** [obj/qwt_interval.o] Error 1
make[1]: Leaving directory `/home/ravi/Desktop/qwt-6.0.0-rc5/src'
make: *** [sub-src] Error 2

what could be the problem? what is the work around?

Thanks in advance.
Aster

---

Added after 6 minutes:

Hi Uwe,

I did not find csv file qt reader code, i found found tar file when googled, but it was empty.

So if you have any link or code please let me know.

Thanks in advance.

BR,
Aster

Even if I would expect that it is unrelated: nobody will answer for qwt-6.0.0-rc5, when there are official Qwt 6.0.x releases for a long time.
Back to your problem: try "type qmake" to see if your qmake is from a Qt version that is compatible with Qwt 6.x.

Uwe

> Do you have any examples which read csv file and plot accordingly?

Posting a question with no example code means that we have to guess what
you might be doing wrong. We can make up answers all day long and never
know if we've told you the real answer. It is like asking "How long is
a piece of string?"

Reading data points from *anywhere* and plotting them using QwtPlot are
completely unrelated problems.

- Have you looked at the arrays of data you are sending to QwtPlot to
see if they actually contain the numbers you see in your CSV file? How
do you know the reading is successful? How do you know the parsing from
string to number is successful?

-- I am able to see the read csv values in the command prompt when I print them on the screen using qDebug() macro.

- If the arrays *do* contain the numbers you expect, how do you allocate
these arrays? The setRawData() method *requires* that the array
pointers be valid for the lifetime of the QwtPlotCurve that is using
them. If your arrays go out of scope before the curve does, then the
curve is trying to use invalid pointers to draw.

--- What class should I use I am not getting QwtSeriesData or QwtArraySeriesData?
---- I have not allocated anything as of now.

- Did you set the axis ranges to match the data ranges? If the data is
outside the range of the plot, then the curve might be drawn, but
nothing is visible because it is outside the axes.

--- I have set the axis ranges according to my data.
----

- Did you set the curve style to be "Lines" and the pen to be something
visible? If the style is set to "NoCurve", then it will be invisible

---I have not set any style to the curve.

Hi ,

I am trying to create graph which is attachedAttachment 7622.
(templog_spec_qwt_post.png)
But as of now the status is like the one attached Attachment 7623.

Please suggest how to get the scales like the one specified(templog_spec), also I want to plot graph dynamically
where the data is coming for every 5 seconds, the data is Time and its corresponding temperature in a csv format.

It may not be smooth sinusoidal curve as the templog_spec is showing.

Thanks in advance.

Aster

Hi

I am now using latest build of qwt-6.0.1 on Ubuntu 10.04, but when tried to install qwt am getting below error:


qmake is /usr/local/Trolltech/Qt-4.7.0/bin/qmake
root@ubuntu:/home/ravi/Desktop/qwt-6.0.1# qmake qwt.pro
root@ubuntu:/home/ravi/Desktop/qwt-6.0.1# make
cd src/ && make -f Makefile
make[1]: Entering directory `/home/ravi/Desktop/qwt-6.0.1/src'
g++ -c -pipe -g -Wall -W -O2 -D_REENTRANT -fPIC -DQT_NO_DEBUG -DQT_THREAD_SUPPORT -DQT_SHARED -DQT_TABLET_SUPPORT -I/usr/share/qt3/mkspecs/default -I. -I/usr/include/qt3 -Imoc/ -o obj/qwt_abstract_scale_draw.o qwt_abstract_scale_draw.cpp
In file included from qwt_scale_div.h:14,
from qwt_abstract_scale_draw.h:14,
from qwt_abstract_scale_draw.cpp:10:
qwt_interval.h:15: fatal error: qdebug.h: No such file or directory
compilation terminated.
make[1]: *** [obj/qwt_abstract_scale_draw.o] Error 1
make[1]: Leaving directory `/home/ravi/Desktop/qwt-6.0.1/src'
make: *** [sub-src-make_default-ordered] Error 2

I think its a well known problem , I did not get any where work around for this. Please help on this.

Thanks in advance.

Aster.

Quote:

---

Originally Posted by Aster036

...-I/usr/share/qt3/mkspecs/default -I. -I/usr/include/qt3 ...

---

Obviously you are trying to build Qwt 6.x with Qt3.

Uwe

Hi Uwe,

Can you please reply on my post which has two images attached.

Thanks in advance.

Hi ,

I tried to download qt csv file from below site:

http://qcsv.svn.sourceforge.net/

but when unzipped the file contains nothing, if you have csv file reader in Qt app download link please share.

Thanks and Regards

Quote:

---

-- I am able to see the read csv values in the command prompt when I print them on the screen using qDebug() macro.

---

You said this in an earlier post. If you are already able to read your data from the CSV file, then why are you wasting time downloading something from SourceForge? An if you go to the SF page you linked to , you will see that it clearly says:

Quote:

---

Files shown: 0

---

so why are you surprised when your tarball is empty?

Posting two images (one of which is clearly something made using a graphics editing program, not with Qwt) and asking "What am I doing wrong?" - How are we supposed to know? You have not shown us ANY SOURCE CODE AT ALL. How are we supposed to guess what you are doing wrong when you have told us absolutely nothing about what you are doing?

Hi ,


Please find the attached files of my application.

Right now I am plotting the graph for 30 hard coded values , but they should be read from the csv files which are added as resources.

Thanks in advance.

Hi

Does anybody has qwt example code which does dynamic plotting ? Please share the same.

Thanks in advance.

I have looked at your code. It is clear to me from the fact that there are more lines of commented out code than there are non-commented lines that you really don't have any idea how to do what you want. I think you are totally confusing things and making it more difficult than it is. From what I understand, you want to do two things:

1 - Read time and temperature strings from a CSV file and convert them to numbers
2 - Create a Qwt plot that displays the temperature vs . time values as a curve

First, you have to understand that reading the data and plotting the data are completely unrelated activities. So don't mix them all up in the same method (or even the same C++ class). Make a C++ class whose job is to read the data file and return the x and y arrays of doubles. It basically needs three methods and a couple of arrays:

Code:

---

class CSVReader
{
public:
CSVReader() {}
 
// opens the CSV file, reads the data into time and temperature arrays, returns true if OK, false otherwise
bool readDataFromFile( const QString & fileName );
 
const QVector<double> & temperature() const { return mTemperature; }
const QVector<double> & time() const { return mTime; }
 
private:
  QVector<double> mTemperature;
  QVector<double> mTime;
};

---

Next, use this class to read the data, then pass the data to your curve:

Code:

---

CSVReader dataSource;
 
if ( dataSource.readDataFromFile( "myfile.csv" ) )
{
   const QVector<double> & temps = dataSource.temperature();
   const QVector<double> & times = dataSource.time();
   curve->setSamples( times.data(), temps.data(), times.size() );  // makes a copy of the data
}

---

That's about as simple as it gets. Please notice, any two QVector<double> instances could be used to build the curve. The fact that the vectors were created by reading a CSV file is completely irrelevant as far as the plot is concerned. A tiny spaceship could land on your PC and a little green man could step out and hand you two vectors, and they would work the same way as far as the plot is concerned.

Hi Stranz,

Thanks a ton for your useful post. :)

I was bit stranded as to what to do and what am I doing wrong?

I shall get back to you if I get some more new problems.

Thank you.
Aster