Q:

excel function "search of the decision function in R

I have the question, whether it is possible in R to implement an excel function "search of the decision"? Is there function in R or it is necessary to create a script in R.
It is necessary to solve the following equation by combining the X values to get 1,126 as the result.
1.126 = X / (X + 0.2) * (EXP (X + 0.2) -1)

A:

You can find the solution to this equation using uniroot. The solution to your equation is the same as the solution to X / (X + 0.2) * (exp(X + 0.2) -1) - 1.126 = 0   So ...
Dec = function(X) X / (X + 0.2) * (exp(X + 0.2) - 1) - 1.126
uniroot(Dec, c(0,2))

(part of) the result is

$root [1]
  0.6959234
  $f.root [1]
  -1.585758e-06

If you need more accuracy,  you can adjust the tol parameter.
uniroot(Dec, c(0,2), tol= 0.0000001)

$root
  [1]  0.6959241
  $f.root
  [1] 7.61391e-13

