Line graph of the mean of all observations

[Toti AL]

Hello all,

I have data that have three variables: vehicle id, speed_kmh, and Time_of_Travel.

I am seeking your help with a code that is capable of calculating the mean of all observations at each travel time (or fixed distance based on the x-axis unit) and then creating a line graph that shows the trend of the observation along with the mean of all observations. An example is shown below for speed vs distance along with my data.

I am using the following code:

xtline speed_kmh , i( vehicleid ) t( timeoftravelall ) overlay leg(off)

if possible, a code works for both cases 1- speed vs time and 2- speed vs distance.

Thank you so much.

Vehicle ID	Speed_kmh	Time_of_Travel
1	80.99	0.00
1	80.99	0.50
1	80.29	1.00
1	78.92	1.50
1	76.87	2.00
1	75.50	2.50
1	74.10	3.00
1	72.67	3.50
1	70.56	4.00
1	69.17	4.50
1	67.75	5.00
1	66.27	5.50
1	64.06	6.00
1	62.59	6.50
1	61.24	7.00
1	60.02	7.50
1	58.21	8.00
1	57.03	8.50
1	55.63	9.00
1	54.03	9.50
1	51.63	10.00
1	50.06	10.50
1	48.23	11.00
1	46.13	11.50
1	42.99	12.00
1	40.90	12.50
1	39.02	13.00
1	37.38	13.50
1	34.90	14.00
1	33.25	14.50
1	31.56	15.00
1	29.84	15.50
1	27.26	16.00
1	25.53	16.50
1	23.74	17.00
1	21.87	17.50
1	19.07	18.00
1	17.21	18.50
1	15.38	19.00
1	13.58	19.50
1	10.89	20.00
1	9.10	20.50
1	8.04	21.00
1	7.72	21.50
1	7.24	22.00
1	6.92	22.50
1	6.26	23.00
1	5.28	23.50
1	3.81	24.00
1	2.83	24.50
1	2.37	25.00
1	2.41	25.50
1	2.49	26.00
1	2.54	26.50
1	2.31	27.00
1	1.81	27.50
1	1.08	28.00
1	0.59	28.50
1	0.34	29.00
1	0.34	29.50
1	0.34	30.00
2	89.11	0.00
2	89.11	0.50
2	88.32	1.00
2	86.75	1.50
2	84.43	2.00
2	82.90	2.50
2	81.78	3.00
2	81.09	3.50
2	80.08	4.00
2	79.43	4.50
2	78.11	5.00
2	76.14	5.50
2	73.21	6.00
2	71.28	6.50
2	69.13	7.00
2	66.76	7.50
2	63.26	8.00
2	60.94	8.50
2	58.31	9.00
2	55.34	9.50
2	50.88	10.00
2	47.91	10.50
2	44.91	11.00
2	41.89	11.50
2	37.37	12.00
2	34.35	12.50
2	31.19	13.00
2	27.91	13.50
2	22.98	14.00
2	19.69	14.50
2	17.45	15.00
2	16.25	15.50
2	14.46	16.00
2	13.27	16.50
2	12.21	17.00
2	11.27	17.50
2	9.86	18.00
2	8.92	18.50
2	7.94	19.00
2	6.94	19.50
2	5.43	20.00
2	4.43	20.50
2	3.63	21.00
2	3.03	21.50
2	2.14	22.00
2	1.54	22.50
2	1.11	23.00
2	0.84	23.50
2	0.47	24.00
2	0.23	24.50
2	0.12	25.00
2	0.12	25.50
2	0.12	26.00
3	86.50	0.00
3	86.50	0.50
3	85.87	1.00
3	84.65	1.50
3	82.85	2.00
3	81.67	2.50
3	80.90	3.00
3	80.54	3.50
3	80.05	4.00
3	79.74	4.50
3	78.74	5.00
3	77.04	5.50
3	74.51	6.00
3	72.85	6.50
3	70.71	7.00
3	68.09	7.50
3	64.22	8.00
3	61.65	8.50
3	58.48	9.00
3	54.67	9.50
3	48.96	10.00
3	45.16	10.50
3	41.55	11.00
3	38.13	11.50
3	33.01	12.00
3	29.59	12.50
3	26.75	13.00
3	24.49	13.50
3	21.10	14.00
3	18.84	14.50
3	16.55	15.00
3	14.24	15.50
3	10.77	16.00
3	8.46	16.50
3	7.19	17.00
3	6.96	17.50
3	6.61	18.00
3	6.38	18.50
3	5.62	19.00
3	4.33	19.50
3	2.39	20.00
3	1.10	20.50
3	0.45	21.00
3	0.45	21.50
3	0.45	22.00