Calculating Interest rate in SQL Server - PPMT / IPMT / PMT

A few days ago I was asked to create simple tool for calculating Interest rate. I received also excel file with all necessary calculations and formulas. Most of formulas used excel financial functions: PPMT , IPMT . I started with googling for SQL port of PPMT but I didnt find anything except this:
SQL Server – Excel Financial Functions – using CLR
Its quite ok, but I noticed that CLR functions are rounded to two decimal plaseces witch was not acceptable for me so I wrote my own functions based on this article: A Guide to the PMT, FV, IPMT and PPMT Functions
Below you will find T-SQL version of  PPMT / IPMT / PMT / FV excel financial functions

 
IF OBJECT_ID('Pmt', 'FN') IS NOT NULL DROP FUNCTION dbo.Pmt  
GO  
CREATE FUNCTION dbo.Pmt (@r NUMERIC(18,4), @nper INT, @pv NUMERIC(18,4), @fv NUMERIC(18,4), @type INT)  
RETURNS NUMERIC(18,4)
AS  
BEGIN  
 DECLARE @pmt NUMERIC(18,4)  
 
 SET @pmt = @r / (Power(1.0 + @r, @nper) - 1.0) * -(@pv * Power(1.0 + @r, @nper) + @fv)  
 
 if @type = 1  
 SET @pmt = @pmt / (1 + @r)  
 RETURN @pmt  
END  
GO  


IF OBJECT_ID('Fv', 'FN') IS NOT NULL DROP FUNCTION dbo.Fv  
GO  
CREATE FUNCTION dbo.Fv (@r NUMERIC(18,4), @nper INT, @c NUMERIC(18,4), @pv NUMERIC(18,4), @type INT)  
RETURNS NUMERIC(18,4)
AS  
BEGIN  
 DECLARE @fv NUMERIC(18,4)  
 
 IF @type = 1  
 SET @c = @c * (1 + @r);  
 
 SET @fv = -(@c * (Power(1 + @r, @nper) - 1) / @r + @pv  
    * Power(1 + @r, @nper))  
 
 RETURN @fv  
END  
GO  

IF OBJECT_ID('Ipmt', 'FN') IS NOT NULL DROP FUNCTION dbo.Ipmt  
GO  
CREATE FUNCTION dbo.Ipmt (@r NUMERIC(18,4), @per INT, @nper INT, @pv NUMERIC(18,4), @fv NUMERIC(18,4), @type INT)  
RETURNS NUMERIC(18,4)   
AS  
BEGIN  
 DECLARE @ipmt NUMERIC(18,4)  
 SET @ipmt = dbo.Fv(@r, @per - 1, dbo.Pmt(@r, @nper, @pv, @fv, @type), @pv, @type) * @r  
 
 if @type = 1  
 SET @ipmt = @ipmt / (1 + @r)  
 RETURN @ipmt  
END  
GO  

IF OBJECT_ID('Ppmt', 'FN') IS NOT NULL DROP FUNCTION dbo.Ppmt  
GO  
CREATE FUNCTION dbo.Ppmt (@r NUMERIC(18,4), @per INT, @nper INT, @pv NUMERIC(18,4), @fv NUMERIC(18,4), @type INT)  
RETURNS NUMERIC(18,4)   
AS  
BEGIN  

 RETURN dbo.Pmt(@r, @nper, @pv, @fv, @type) - dbo.Ipmt(@r, @per, @nper, @pv, @fv, @type);  

END  
GO