How to generate value look like a line

I want to generate more value between certain of range data, below is my data
X Y
0.5044 0.4344
0.491721 0.432822
0.4811 0.4315
0.491673 0.414895
0.4701 0.4128
0.4798 0.3967
0.46945 0.3954
0.4591 0.3941
This data when generate 8 dots in the graph, I want to create more value between each data so that the data look it show like a rectangular box. I manually create some of the data between the first two row for X and Y, example
X Y
0.5044 0.4344
0.5022 0.434<-added
0.495 0.4333<-added
0.4988 0.4338<-added
0.502 0.43<-added
0.499 0.425<-added
0.4953 0.42<-added
0.491721 0.432822
I want more value to link the data together, so the graph look like a line between the dots. Isn't possible to do in such way?