Regarding to studies in different countries the research and development (R&D) play a major role in economy growth. Investment in R&D increase level of knowledge, and we have increase in production efficiency by knowledge increasing, after that economic growth will improve by productivity channel. Many studies exist on the R&D but in any of them not used the same variable for this indicator. The time series of knowledge level is not visible because of complexity the calculations and measurements of this variable. In this study the level of knowledge is intended as an unobservable variable. After that using LP and OP method the time series of this variable is extracted during the period 1974-2014 for Iranian economy. Estimates this series will be an important way for future empirical studies in research and development. Algorithms and methods that used in this paper can be run for other countries. Based on LP method, results shows during the 40 years of knowledge for Iranian economy has upward trend and the averages of grow rate of knowledge level is 0.42 percent for each year.