# Interpolate dates along a line

I have a `road_condition` table in Oracle 12c:

``````create table road_condition (
cond_id number(5,0),
cond_date date,
condition number(5,0)
);

values (1,100,to_date('01-NOV-84','DD-MON-RR'),18);
values (2,100,to_date('01-JAN-09','DD-MON-RR'),6);
values (3,100,to_date('19-JUN-12','DD-MON-RR'),4);
values (4,100,to_date('29-APR-15','DD-MON-RR'),4);
values (5,200,to_date('29-APR-92','DD-MON-RR'),20);
values (6,200,to_date('05-APR-17','DD-MON-RR'),3);
commit;
``````

Resulting table data:

``````COND_ID ROAD_ID   COND_DAT CONDITION
------- -------   -------- ---------
1     100   84-11-01        18
2     100   09-01-01         6
3     100   12-06-19         4
4     100   15-04-29         4
5     200   92-04-29        20
6     200   17-04-05         3
``````

Here is a graph of road `#100`:

`Condition` in the table is categorized like this:

• 20 to 15 is in Good condition and does not require any treatment
• 14 to 11 requires an Overlay treatment
• 10 to 8 requires a Full Depth Removal (FDR) treatment
• 7 to 0 requires Reconstruction treatment

`Condition` is from 0 to 20, 20 being a perfect road.

When roads are inspected, the condition is stored as a whole number(integer), never as a decimal.

Question:

Rather than show the line in the graph as a single colour (blue), I would like to stripe the line as coloured categories.

I've mocked up `road #100` in Excel:

Idea:

To stripe/categorize the data as described, I think I need to create dummy points (rows) at the beginning and end of each range along the line.

Perhaps the simplest way to do this would be to create points (rows) at all intervals of condition, instead of just at the beginning and end of each range.

The graphing software that I'm using creates a new line in the graph for each Y-column/series (similar to the way Excel does).

Therefore, I believe I need each category to be isolated in a separate column, so it can be drawn as a separate line (with a separate colour).

Additionally, there needs to be overlap between each category, so that the graphing software does not display gaps between lines.

How can I create the dummy rows (interpolate the dates)?

Update:

I have a related question here: Date as x-axis: How to multiply and divide dates?

• at this point just questions ... 1) how do you (programmatically) determine the `COND_DATE` values for the boundary rows? 2) do you need a set of boundary rows for each distinct `road_id` (ie, what's the desired output look like if you add some rows for `road_id=200`)? 3) why do the lower limits (15, 11, 8) get placed in 2 diff treatment columns but the upper limits (14,10, 7) only get placed in one column (ie, the previously mentioned categories don't show condition #s w/ more than one treatement)? 4) have you looked at how to pivot rows to columns (both in pl/sql and excel)? – markp Nov 26 '17 at 0:27
• fwiw ... quick google search on "excel conditional formatting graph line colors" brings up change chart color... and ~40% way down page is a graph that looks very similar to what you want to do ... so wondering if you might be able get (close to) what you want without adding the new records ... ?? – markp Nov 26 '17 at 0:47
• as drawn it looks like you have 10 measurements (instead of the actual 4 measurements); wondering if perhaps it's possible to stick with just the 4 measurement points but colorize the background/chart (short of some extensive testing in excel, I'm making a wild guess that something like would be doable within excel); so, a green band (left to right) @ top of chart, then yellow band, red and then dark red (brown?) ... would be easy to visually see when your plot line crosses between the colored ranges ... ? you could then save the different color plot lines for different roads – markp Nov 26 '17 at 0:58
• @markp Smart idea. I had tried this, but ultimately found it dizzying/too much to look at. So I thought I'd try the striped lines. Also, the graph was an easy example to use in the question, but in addition to graphing, having the boundary rows would be quite useful in tabular analysis. – Wilson Nov 26 '17 at 1:05

Have fun.

``````with
num_years as (select extract(year from max(cond_date)) - extract(year from min(cond_date)) +1 as years from road_condition where road_id = 100),
generated_dates as (select add_months(trunc((select min(cond_date) from road_condition where road_id = 100), 'YYYY'), (rownum - 1) * 12) as cond_date from dual connect by level <= (select years from num_years)),
generated_data as (select rc.cond_id, rc.road_id,nvl(rc.cond_date, gd.cond_date) as cond_date, rc.condition
from generated_dates gd left join (select * from road_condition where road_id = 100) rc on (gd.cond_date = trunc(rc.cond_date, 'YYYY'))
),
data1 as (select
last_value(cond_id ignore nulls) over (order by cond_date) as cond_id,
cond_id as original_cond_id,
last_value(condition ignore nulls) over (order by cond_date) as s1,
lead(condition ignore nulls) over (order by cond_date) as s2
from generated_data
),
data2 as (
select
cond_id, road_id, original_cond_id, cond_date, condition, s1, s2,
count(*) over (partition by cond_id) + 1 as s,
count(*) over (partition by cond_id order by cond_date rows between unbounded preceding and current row) as s0
from data1
),
data3 as (
select original_cond_id as cond_id, road_id, cond_date,
round(nvl(condition, (1-s0/s)*(s1-s2)+s2)) as condition
from data2
),
final_data as (
select cond_id, road_id, cond_date,
case when condition between 15 and 20 then condition end as cond_good,
case when condition between 11 and 14 then condition end as cond_overlay,
case when condition between 8 and 10 then condition end as cond_fdr,
case when condition between 0 and 7 then condition end as cond_recon
from data3
),
data_for_graph as
(
select
cond_id, road_id, cond_date, cond_good,
case when cond_good is not null and lead(cond_overlay) over (order by cond_date) is not null then cond_good else cond_overlay end as cond_overlay,
case when cond_overlay is not null and lead(cond_fdr) over (order by cond_date) is not null then cond_overlay else cond_fdr end as cond_fdr,
case when cond_fdr is not null and lead(cond_recon) over (order by cond_date) is not null then cond_fdr else cond_recon end as cond_recon
from final_data
)
select * from data_for_graph order by cond_date;
``````

Output:

``````   COND_ID    ROAD_ID COND_DATE   COND_GOOD COND_OVERLAY   COND_FDR COND_RECON
---------- ---------- ---------- ---------- ------------ ---------- ----------
1        100 1984-11-01         18
1985-01-01         17
1986-01-01         17
1987-01-01         16
1988-01-01         16
1989-01-01         15
1990-01-01         15           15
1991-01-01                      14
1992-01-01                      14
1993-01-01                      13
1994-01-01                      13
1995-01-01                      12
1996-01-01                      12
1997-01-01                      12
1998-01-01                      11
1999-01-01                      11         11
2000-01-01                                 10
2001-01-01                                 10
2002-01-01                                  9
2003-01-01                                  9
2004-01-01                                  8
2005-01-01                                  8          8
2006-01-01                                             7
2007-01-01                                             7
2008-01-01                                             6
2        100 2009-01-01                                             6
2010-01-01                                             5
2011-01-01                                             5
3        100 2012-06-19                                             4
2013-01-01                                             4
2014-01-01                                             4
4        100 2015-04-29                                             4
``````

You can follow the steps by selecting from the CTEs in the last line in the order I listed them (so `select * from num_years`, then `select * from generated_dates`, then `select * from generated_data`, and so on).

• Balazs, In my original question, the `road_id` was only to be returned for the first row for each of the original records. Your query does this. Thanks. However, I realize in hindsight that that's not quite what I need. How difficult would it be to change your query so that it returns the `road_id` for all records? – Wilson Nov 30 '17 at 14:06

Here's a solution developed in SQL Server 2008 R2 that uses Window Functions, which may not translate well to Oracle 12c.

It has the advantage of only spitting out the exact number of dates needed to plot each coloured line segment on the graph.

Set up temp table:

``````IF OBJECT_ID('tempdb.dbo.#road_condition') IS NOT NULL DROP TABLE #road_condition;

CREATE TABLE #road_condition (
cond_id int
,cond_date DATE
,condition int
);

``````

``````SELECT DISTINCT
,CONVERT(DATE,
CONVERT(DATETIME, rcStart.cond_date)
+ (ROW_NUMBER() OVER (PARTITION BY rcStart.road_id, rcStart.cond_date ORDER BY Conditions.Condition DESC) - 1)
* DATEDIFF(DAY, rcStart.cond_date, rcEnd.cond_date)
/ CASE WHEN COUNT(1) OVER (PARTITION BY rcStart.road_id, rcStart.cond_date) = 1 THEN 1
ELSE (COUNT(1) OVER (PARTITION BY rcStart.road_id, rcStart.cond_date) - 1) END
) AS StepDate
,Good, Overlay, FDR, Recon
AND rcEnd.cond_id = rcStart.cond_id + 1
LEFT JOIN (
SELECT TOP 21 ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) - 1 AS Condition
FROM sys.columns
) AS Conditions ON Conditions.Condition BETWEEN rcEnd.condition AND rcStart.condition
LEFT JOIN (SELECT * FROM (VALUES (20),(19),(18),(17),(16),(15)) v(Good)) Good ON Good = Conditions.Condition
LEFT JOIN (SELECT * FROM (VALUES (15),(14),(13),(12),(11)) v(Overlay)) Overlay ON Overlay = Conditions.Condition
LEFT JOIN (SELECT * FROM (VALUES (11),(10),(9),(8)) v(FDR)) FDR ON FDR = Conditions.Condition
LEFT JOIN (SELECT * FROM (VALUES (8),(7),(6),(5),(4),(3),(2),(1),(0)) v(Recon)) Recon ON Recon = Conditions.Condition
``````

The Output:

The Graph:

• Oreo, thanks for your answer. A couple of questions: 1) I don't understand why there is a slight curve in the line between 2006 and 2009. Shouldn't the line be straight between 1984 and 2009, since there aren't any other inspections in the table between those two dates? I get the same result when I graph the query from my answer too. 2) Is the last inspection for road #100 from 2015 missing from your query/graph? – Wilson Nov 30 '17 at 15:21
• Wilson, something like that, I think there's an off-by-one bug in the gradient calculation, as it ends up steeper than it should be, by 13/12... I'll have a look when I can. – Oreo Nov 30 '17 at 15:56
• I'm not sure, but I think the bend in the line might be caused by the `base` setting in the graph in Excel (or whatever you're using). I had a similar problem, and I solved it by switching from `base=years` to `base=days`. Screencap: i.stack.imgur.com/G7wg8.png – Wilson Nov 30 '17 at 20:58
• Nah, it's definitely a bug in my code. If you check the Results table, the space from quality 8 to 7 is 2 years, but 7 to 6 is 3 years. Those should be the same spacing. – Oreo Dec 1 '17 at 10:09

This one is `Sql server` version and it can be easily translated to `Oracle`.

My script find data for each month.

Formula of calculating condition is very clear from script.

I am using table calendar in script,which contain first Day of month.

I am using temp table but in real life it is permanent table

Above all, though condition is `int` in table but to populate graph it can be `decimal`

Sample data,

``````CREATE TABLE #road_condition (
cond_id int
,cond_date DATE
,condition int
);

``````

calender table can be created with one own logic.

``````create table #tblCal(FOM date not null)
insert into #tblCal
select DATEADD(MONTH, ROW_NUMBER()over(order by number)-1,'1900-01-01')
from master..spt_values

;With CTE as
(
,MinCond,Maxcond
,round(((Maxcond-MinCond) /
cast(DATEDIFF(month,MinDate,MaxDate) as float)),2) MagicNumber

from #tblCal tbl

cross apply(
select road_id, MIN(rc.cond_date) MinDate, MAX(rc.cond_date) MaxDate
, MIN(rc.condition) MinCond, MAX(rc.condition) Maxcond
) ca
where tbl.FOM between MinDate AND MaxDate
--and rn=1
)
,CTE1 AS
(
,MinDate,maxdate
--,d
,MagicNumber
,ROW_NUMBER()over(PARTITION by cond_id order by fom)rn1
,condition,cond_id,cond_date
from cte c
outer APPLY (select top 1
rc.condition,rc.cond_id,cond_date
and ((month(fom)=month(rc.cond_date) and  YEAR(fom)=YEAR(rc.cond_date))
or ((month(fom)!=month(rc.cond_date) or YEAR(fom)!=YEAR(rc.cond_date)) and cond_date<fom))
order by rc.cond_date DESC
)ca
)
,CTE2 AS(
,case when (month(fom)=month(cond_date) and  YEAR(fom)=YEAR(cond_date))
THEN condition
ELSE
condition-(rn1*MagicNumber)
end condition
from cte1
)

,case when condition between 15 and 20 then condition end as cond_good,
case when condition between 11 and 15 then condition end as cond_overlay,
case when condition between 8 and 11 then condition end as cond_fdr,
case when condition<=8 then condition end as cond_recon
from cte2

drop table #tblCal
``````

I think I might have cracked it, with this relatively simple approach.

It assumes that the road age is known, rather than the condition date. More information here: Date as x-axis: How to multiply and divide dates?

It uses simple math to get the slope and y-intercept of each segment of the linestring. Then cross joins to a numbers table (condition numbers) to generate points at each interval of condition.

``````create table numbers_condition
(
numbers number(4,0)
);
insert into numbers_condition numbers values (20);
insert into numbers_condition numbers values (19);
insert into numbers_condition numbers values (18);
insert into numbers_condition numbers values (17);
insert into numbers_condition numbers values (16);
insert into numbers_condition numbers values (15);
insert into numbers_condition numbers values (14);
insert into numbers_condition numbers values (13);
insert into numbers_condition numbers values (12);
insert into numbers_condition numbers values (11);
insert into numbers_condition numbers values (10);
insert into numbers_condition numbers values (9);
insert into numbers_condition numbers values (8);
insert into numbers_condition numbers values (7);
insert into numbers_condition numbers values (6);
insert into numbers_condition numbers values (5);
insert into numbers_condition numbers values (4);
insert into numbers_condition numbers values (3);
insert into numbers_condition numbers values (2);
insert into numbers_condition numbers values (1);
insert into numbers_condition numbers values (0);
commit;
``````

``````with a as
(
select
cond_id,
x1,
y1,
x2,
y2,
(y2-y1)/(x2-x1) as m_slope,
y1-((y2-y1)/(x2-x1))*x1 as y_intercept
from
(
select
cond_id,
cond_date - to_date('1980-01-01', 'YYYY-MM-DD') as x1,
condition as y1,
lead(cond_date - to_date('1980-01-01', 'YYYY-MM-DD')) over (partition by road_id order by cond_date) as x2,
lead(condition,1,condition)                           over (partition by road_id order by cond_date) as y2
from
)
)
select distinct
case when m_slope <> 0 then ((b.numbers - y_intercept)/m_slope) + to_date('1980-01-01', 'YYYY-MM-DD') else a.x1 + to_date('1980-01-01', 'YYYY-MM-DD') end as cond_date,
case when b.numbers between 15 and 20 then b.numbers end as cond_good,
case when b.numbers between 11 and 15 then b.numbers end as cond_overlay,
case when b.numbers between 8 and 11 then b.numbers end as cond_fdr,
case when b.numbers between 0 and 8 then b.numbers end as cond_recon
from
a
cross join
numbers_condition b
where
b.numbers between a.y1 and a.y2
or b.numbers between a.y2 and a.y1
order by
cond_date
;
``````

Note: I couldn't figure out how to set up the `where` clause to get only the records that I want from the cross join (a few junk/duplicate records get output to the result set). It gets a bit complicated when there are line segments that have no slope or have a positive slope. So I took the easy way out and just eliminated the duplicates by `selecting distinct`.

``````   ROAD_ID COND_DAT  COND_GOOD COND_OVERLAY   COND_FDR COND_RECON
---------- -------- ---------- ------------ ---------- ----------
100 84-11-01         18
100 86-11-06         17
100 88-11-11         16
100 90-11-16         15           15
100 92-11-21                      14
100 94-11-26                      13
100 96-12-01                      12
100 98-12-07                      11         11
100 00-12-11                                 10
100 02-12-17                                  9
100 04-12-21                                  8          8
100 06-12-27                                             7
100 09-01-01                                             6
100 10-09-25                                             5
100 12-06-19                                             4
100 15-04-29                                             4

200 92-04-29         20
200 93-10-16         19
200 95-04-05         18
200 96-09-22         17
200 98-03-11         16
200 99-08-29         15           15
200 01-02-15                      14
200 02-08-04                      13
200 04-01-22                      12
200 05-07-11                      11         11
200 06-12-29                                 10
200 08-06-16                                  9
200 09-12-04                                  8          8
200 11-05-24                                             7
200 12-11-09                                             6
200 14-04-29                                             5
200 15-10-17                                             4
200 17-04-05                                             3
``````

Inspired by other answers to this question and by a previous question I had here: Cross join on a numbers table to get line vertices, is there a better way?

• For my records: to make up for some limitations in my graphing software, it helps to add some dummy/blank records at the beginning and end of each line... – Wilson Dec 1 '17 at 21:04
• ... `union all select road_id, to_date(extract(year from min(cond_date)) || '-01-01', 'yyyy-mm-dd') as cond_date, null as cond_good, null as cond_overlay, null as cond_fdr, null as cond_recon from road_condition group by road_id` – Wilson Dec 1 '17 at 21:04