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2015-05-25 03:40:25 -0500 received badge  Famous Question (source)
2014-01-28 17:27:42 -0500 marked best answer Problem in my ROS answers profile

I cannot see the option "post a comment" in most of the places. For example, I posted a question few mins ago. I got two answers for that but I am unable to see the option post a comment below the answers. But I can see the comment option below my question. So, I would like to know how to solve this problem.?

2014-01-28 17:26:49 -0500 marked best answer Error in $ rosmake rgbdslam with ros-electric

I am using ros-electric. When I build rgbdslam package in ros.

$ rosmake rgbdslam.

I got the error,

/usr/bin/ld: CMakeFiles/rgbdslam.dir/src/openni_listener.o: in function OpenNIListener::processNode(Node*):openni_listener.cpp(.text+0x6fd4): error: undefined reference to 'clock_gettime'

Anybody have idea about this?

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2013-07-26 03:49:32 -0500 commented answer Any packages for graph plot?

I need anything such that I should plot values of various variables while the program is running i.e)dynamically.

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2013-07-22 23:56:44 -0500 commented answer Any packages for graph plot?

But 'matplotlib' is in python. I need to access the c++ outputs dynamically. and Is there any with c++ ? or Is it possible to use matplotlib for accessing c++ outputs dynamically ?

2013-07-22 16:22:38 -0500 received badge  Popular Question (source)
2013-07-22 06:11:02 -0500 asked a question Any packages for graph plot?

Hello everybody,

Is there any packages available with ROS for 2d or 3d plotting of mathematical data (if possible, something similar to matlab plotting) ?

NOTE: I need to access the c++ output data dynamically for plotting.

2013-07-22 06:06:23 -0500 received badge  Popular Question (source)
2013-06-27 04:01:26 -0500 asked a question how to find correlation coefficient for two images?

I have two 16-Bit grey level images in cv::Mat format. I just have to find the correlation coefficient scores i.e) a score says how much the two images match each other.

Is there any functions in opencv or any other libraries to find it?

Exception Note: I cannot link gsl library to my project.

2013-02-02 04:16:42 -0500 received badge  Teacher (source)
2012-10-31 19:03:14 -0500 marked best answer Is there any tutorials for visual SLAM (beginners)?

Hello,

I am new to ros as well as to robotics. I wish to learn some basic tutorials in Visual-SLAM. I tried RGBDSLAM from ros and it works. As I am not good in programming, I can't understand the codes.

So, I would like to learn how to do programming for visual SLAM (c++ or Matlab). Is there any available tutorials for visual SLAM (any webpages or books)?

2012-10-18 04:41:57 -0500 marked best answer publisher and subscriber in single node

Consider node 'x' publishes topic 'a' and 'b'. Now, I should create a node 'y' to subscribe a topic 'a'. Then the subscribed topic should be edited and published again in the name 'c'.

I tried,

// some part of the codes

void chattercallback(const .... )
{

.........

// edit or process the subscribed value<
//to publish the edited data

ros::Publisher d =......;

d.publish(..) ;

....}

int main (int argc, char **argv){

ros::init (..);

ros::Subscriber sub = .....(.. , .. , chattercallback);

....

}

But, the data is not published continuously. This node publishes data only when the topic 'a' is available i.e) only when the data is subscricbed. I need to change this codes such that data is to be published continuously i.e) even if the subscriber does not subscribe any data, it should publish the data according to the last subscribed one.

Is there any ideas for this problem?


I cannot find the option 'post a comment' below the answers. So I will post it here.

But the problem is how to access the value in topic 'a' for storing it to a variable?

2012-10-18 04:41:52 -0500 commented answer publisher and subscriber in single node

Already, I declared my pub as a class member. So, I expect this should be problem with the other node subscribing this one..

2012-10-18 03:55:13 -0500 commented answer publisher and subscriber in single node

In my code, the publisher is data member of the class. So, I think when it enters the callback function it will not be destroyed (callback is the member function of the same class)

2012-10-17 22:24:01 -0500 commented answer publisher and subscriber in single node

thats why I am asking where to put the spin loop. Also, In your answer, I didn't understand 'Calling "publish" doesn't put the data on the topic, so if you destroy publisher before the data is send, you lose the information stored in the buffer'

2012-10-17 22:23:28 -0500 commented answer publisher and subscriber in single node

I subscribe a point cloud data into this node. If I write a main function as mentioned above without a spin in main function, it gives an error because the subscribed data will be available only at some particular point of time. In case of spin loop inside the main function it will not give error.

2012-10-17 21:58:56 -0500 commented answer publisher and subscriber in single node

I used callback function as a class member and store data from callback function into a data member. I do publishing in the main function within a while loop (loop has ros::spinOnce). But, I cannot understand what is explicit spin loop and where to put the spin loop in the main function.

2012-10-17 07:18:40 -0500 commented answer publisher and subscriber in single node

But, I have a doubt where to put the ros::spin for callback function of the subscriber? If I write a code as mentioned above, I can view the required data inside the while loop. By calling the function publish, data is not put into the topic. I don't know why it happend.