Retrieving a specific index of array in d3 select

The following selects all the elements from the array connections. I just want a particular one.

var route = vis.selectAll("line.route")
.data(connections)
.enter().append("svg:line")
  .attr("class", "route")
  .attr("stroke", function(d) { return '#'+routesById[d.line].colour; })
  .attr("stroke-linecap", 'round')
  .attr("x1", function(d) { return x(d.station1.longitude); })
  .attr("y1", function(d) { return y(d.station1.latitude); })
  .attr("x2", function(d) { return x(d.station2.longitude); })
  .attr("y2", function(d) { return y(d.station2.latitude); })

connections is an array(i think) and on the console is defined as

[Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object…]

However I only want to select an element at a particular index. I tried to use the filter but it did not work?

.data(connections.filter(function(d) { return d[23] }))