-- first int2
SELECT vec_to_first(smallints ORDER BY sensor_id) AS firsts
FROM measurements;
 firsts  
---------
 {1,2,3}
(1 row)

-- first int4
SELECT vec_to_first(ints ORDER BY sensor_id) AS firsts
FROM measurements;
 firsts  
---------
 {1,2,3}
(1 row)

-- first int8
SELECT vec_to_first(bigints ORDER BY sensor_id) AS firsts
FROM measurements;
 firsts  
---------
 {1,2,3}
(1 row)

-- first float4
SELECT vec_to_first(reals ORDER BY sensor_id) AS firsts
FROM measurements;
 firsts  
---------
 {1,2,3}
(1 row)

-- first float8
SELECT vec_to_first(floats ORDER BY sensor_id) AS firsts
FROM measurements;
 firsts  
---------
 {1,2,3}
(1 row)

-- first numeric
SELECT vec_to_first(nums ORDER BY sensor_id) AS firsts
FROM measurements;
      firsts      
------------------
 {1.23,2.34,3.45}
(1 row)

-- first numeric 2
SELECT vec_to_first(data_i ORDER BY ts) AS firsts
FROM measurements2;
                                firsts                                
----------------------------------------------------------------------
 {31,-1.348291,228.79181,49.664787,3021,0.99999994,-23.358469,3021,1}
(1 row)

-- first numeric 3
SELECT vec_to_first(pad_vec(data_a, 3) ORDER BY ts) AS firsts
FROM measurements2;
        firsts         
-----------------------
 {6255484,NULL,61.765}
(1 row)

-- first text
SELECT vec_to_first(vals) FROM (VALUES (ARRAY[NULL,'a','foo']::text[]), (ARRAY['one','b','bar']::text[]), (ARRAY['two','c',NULL]::text[])) t(vals);
 vec_to_first 
--------------
 {one,a,foo}
(1 row)