How to publish float64 array to a topic?

edit

Hello, I am trying to publish fake joint states on a topic. My code compiles successfully, however, it gives an error "Segmentation fault, core dumped" when is run the node. Basically, I want to publish two fake positions (0) and two velocities.

#include<ros/ros.h>
#include<std_msgs/Float64.h>
#include <sensor_msgs/JointState.h>
float lVel = 0, rVel = 0, lPos = 0, rPos = 0;

int main(int argc, char** argv){
    ros::init(argc, argv, "custom_joint_state_publisher");
    ros::NodeHandle n;
    ros::Publisher statePub = n.advertise<sensor_msgs::JointState>("measured_joint_states", 100); 
    sensor_msgs::JointState joint_values;
    ros::Rate r(10);
    while(ros::ok()){
        joint_values.header.stamp = ros::Time::now();
        joint_values.position[0] = 0 ;
        joint_values.position[1] = 0;
        joint_values.velocity.push_back(0);
        joint_values.velocity.push_back(0);
        statePub.publish(joint_values);
        r.sleep();
        ros::spinOnce();
    }
    return 0;
}

Here you can see that I am using the assignment operator and pushback() function. The segmentation fault error appears with the assignment operator only. The issue with push_back function is that instead of publishing one value (0), it publishes multiple values (array of 0s) on the topic. How to publish one 0 at a time to the topic? I am using ROS melodic, Ubuntu 18.04. Thank you!