Creating continous tf broadcaster with Boost::Thread

edit

This is a bit of a continuation from a previous question here:here.

Basically, I want to create a class that allows me to continuously publish frames to tf. I have no experience at all in multithreaded programming, but I found a decent introduction to Boost that I have been referencing. I have gotten my code to compile, but when I try to use the plotf() method it spits out the following error:

Adding a frame to be plotted
Creating broadcasting thread
Broadcasting 1 transforms    
[FATAL] [1406225580.899040462]: ASSERTION FAILED
        file = /opt/ros/hydro/include/ros/publisher.h
        line = 108
        cond = false
        message = 
    [FATAL] [1406225580.899232266]: Call to publish() on an invalid Publisher (topic [/tf])
    [FATAL] [1406225580.899378655]:

Here is my header file:

  #ifndef UTILITIES_H
#define UTILITIES_H

#include <Eigen/Core>
#include <tf/transform_broadcaster.h>
#include <boost/thread.hpp>

class RvizPlotter{


    class RvizFrame{
        public:
            std::string parentName;
            std::string childName;
            tf::Transform frame;
            RvizFrame(tf::Transform frame, std::string parentName, std::string childName);
    };
std::vector<RvizFrame> frames;
tf::TransformBroadcaster br;

void broadcast();

public:
    RvizPlotter(int argc, char **argv);
    void plotf(Eigen::Matrix4f f, std::string parentName, std::string childName);
    void plotf(Eigen::Matrix4f f, std::string frameName);
};

#endif

And here is the source file:

#include <ros/ros.h>
#include <Eigen/Core>
#include <tf/transform_broadcaster.h>
#include <tf/transform_listener.h>
#include <ur5/utilities.h>

RvizPlotter::RvizFrame::RvizFrame(tf::Transform frame, std::string parentName, std::string childName){
  this->frame = frame; this->parentName = parentName; this->childName = childName;
}

void RvizPlotter::plotf(Eigen::Matrix4f h, std::string parentName, std::string childName){
  printf("Adding a frame to be plotted\n");
  tf::Transform frame;
  frame.setOrigin(tf::Vector3(h(0,3), h(1,3), h(2,3)));
  frame.setBasis(tf::Matrix3x3(h(0,0), h(0,1), h(0,2),
                               h(1,0), h(1,1), h(1,2),
                               h(2,0), h(2,1), h(2,2)));
  frames.push_back(RvizPlotter::RvizFrame(frame, parentName, childName));
}

void RvizPlotter::plotf(Eigen::Matrix4f h, std::string frameName){
  plotf(h,"map",frameName);
}

void RvizPlotter::broadcast(){
  printf("Broadcasting %d transforms\n",frames.size());
  while(frames.size() > 0)
  {
    for(int i = 0; i < frames.size(); i++){
      br.sendTransform(tf::StampedTransform(frames[i].frame, ros::Time::now(), frames[i].parentName, frames[i].childName));
    }
  }
  boost::this_thread::sleep(boost::posix_time::millisec(100));
}

RvizPlotter::RvizPlotter(int argc, char **argv){
  ros::init(argc, argv, "plotter");
  ros::NodeHandle node;

  //Testing that frames do actually get pushed into vector
  Eigen::Matrix4f h = Eigen::MatrixXf::Identity(4,4);
  plotf(h,"Frame");

  printf("Creating broadcasting thread\n");
  boost::thread* broadcastThread = new boost::thread(boost::bind(&RvizPlotter::broadcast, this));
}

Any ideas on what I'm doing wrong?