The correct answer is option (b) - collection of foreign institutional data.

**Explanation:**

The Reserve Bank of India (RBI) is the central bank of India and plays a crucial role in the Indian economy. It was established on April 1, 1935, under the Reserve Bank of India Act, 1934, and nationalized in 1949. RBI performs various functions to regulate and control the banking system and monetary policy in India.

Let's discuss the functions of RBI in detail:

**a) Promoting Banking:**
RBI promotes the growth and development of the banking system in India. It formulates policies and regulations to ensure the stability, soundness, and efficiency of the banking sector. It issues licenses for the establishment of new banks, sets guidelines for their functioning, and regulates their operations. RBI also acts as the lender of last resort to banks, providing them with liquidity support when needed.

**b) Collection of Foreign Institutional Data:**
This option is incorrect as RBI does collect foreign institutional data. RBI is responsible for collecting and maintaining data related to foreign institutional investments (FIIs) and foreign direct investments (FDIs) in India. This data helps in monitoring capital flows, analyzing market trends, and formulating policies related to foreign investments.

**c) Banker to Government:**
RBI acts as a banker to the central and state governments. It manages their banking transactions, maintains their accounts, and provides them with short-term credit facilities. RBI also manages the government's public debt, issuing and managing government securities, and conducting auctions for their sale. It plays a crucial role in managing the government's cash flow and ensuring the stability of the financial system.

**d) Funding to NABARD:**
RBI provides financial support and funding to the National Bank for Agriculture and Rural Development (NABARD). NABARD is a development bank that focuses on providing credit and financial services to the agriculture sector and rural areas. RBI provides funds to NABARD for its operations, refinancing of loans, and implementing various rural development programs.

In conclusion, the function of RBI that is not correct is the collection of foreign institutional data. RBI does collect and maintain data related to foreign institutional investments and plays a significant role in promoting banking, acting as a banker to the government, and funding NABARD.