Alyssa Columbus published maintains this GitHub repository with a great tutorial on how to move from Excel to R. Very useful for beginning useRs, the repository’s tutorial includes a translation table between Excel and R functions:

Excel Formula	R Function	Type
ABS	abs	Arithmetic
ADDRESS	assign	Essentials
AND	&,&&,all	Boolean
AVERAGE, AVG, AVERAGEIF	mean	Arithmetic
BETADIST	pbeta	Statistics
BETAINV	qbeta	Statistics
BINOMDIST	pbinom when cumulative,dbinom when not	Statistics
CEILING	ceiling	Arithmetic
CELL	str has the same idea	Essentials
CHIDIST, CHISQDIST	pchisq	Statistics
CHIINV, CHISQINV	qchisq	Statistics
CHITEST	chisq.test	Statistics
CHOOSE	switch	Essentials
CLEAN	gsub	Text
COLS, COLUMNS	ncol	Essentials
COLUMN	col,:,seq	Essentials
COMBIN	choose	Essentals
CONCATENATE	paste	Text
CONFIDENCE	-qnorm(alpha/2)*std/sqrt(n)	Statistics
CORREL	cor	Statistics
COUNT, COUNTIF	length	Arithmetic
COVAR	cov	Statistics
CRITBINOM	qbinom	Statistics
DELTA	identical	Boolean
EXACT	==	Boolean
EXP	exp	Arithmetic
EXPONDIST	pexp when cumulative,dexp when not	Statistics
FACT	factorial	Arithmetic
FACTDOUBLE	dfactorial in the phangorn package	Arithmetic
FDIST	pf	Statistics
FIND	regexpr,grepl,grep	Text
FINV	qf	Statistics
FISHER	atanh	Arithmetic
FISHERINV	tanh	Arithmetic
FIXED	format,sprintf,formatC	Essentials
FLOOR	floor	Arithmetic
FORECAST	predict on an lm object	Statistics
FREQUENCY	cut,table	Arithmetic
FTEST	var.test	Statistics
GAMMADIST	pgamma if last argument T,dgamma if last arg. F	Statistics
GAMMAINV	qgamma	Statistics
GAMMALN	lgamma	Statistics
GAUSS	pnorm(x) - 0.5	Statistics
GCD	gcd	Arithmetic
GEOMEAN	exp(mean(log(x)))	Arithmetic
GESTEP	>=	Boolean
HARMEAN	harmonic.mean in the psych package	Arithmetic
HLOOKUP	match,merge	Essentials
HYPGEOMDIST	dhyper	Statistics
IF	if,ifelse	Essentials
IFERROR	try,tryCatch	Essentials
INDEX	x[y,z]	Essentials
INDIRECT	get	Essentials
INT	as.integer(not for negative numbers),floor	Arithmetic
INTERCEPT	first element of coef of an lm object	Statistics
ISLOGICAL	is.logical	Boolean
ISNA	is.na	Boolean
ISNUMBER	is.numeric	Boolean
ISTEXT	is.character	Boolean
KURT	kurtosis in the moments package	Statistics
LARGE	sort	Statistics
LCM	scm in the schoolmath package	Arithmetic
LEFT	substr	Text
LEN, LENGTH	nchar	Text
LINEST	lm	Statistics
LN, LOG	log	Arithmetic
LOG10	log10	Arithmetic
LOGINV	qlnorm	Statistics
LOGNORMDIST	plnorm	Statistics
LOWER	tolower	Text
MATCH	match,which	Essentials
MAX	max (sometimes pmax)	Arithmetic
MDETERM	det	Arithmetic
MEDIAN	median	Arithmetic
MID	substr	Text
MIN	min (sometimes pmin)	Arithmetic
MINVERSE	solve	Arithmetic
MMULT	%*%	Arithmetic
MOD	%%	Arithmetic
MODE	as.numeric(names(which.max(table(x))))	Arithmetic
MUNIT	diag	Arithmetic
N	as.numeric	Arithmetic
NEGBINOMDIST	dnbinom	Statistics
NORMDIST, NORMSDIST	pnorm when cumulative,dnorm when not	Statistics
NORMINV, NORMSINV	qnorm	Statistics
NOT	!	Boolean
NOW	date,Sys.time	Essentials
OR	`	,
PEARSON	cor	Statistics
PERCENTILE	quantile	Statistics
PERCENTRANK	ecdf	Statistics
PERMUT	function(n,k) {choose(n,k)*factorial(k)}	Arithmetic
PERMUTATIONA	n^k	Arithmetic
PHI	dnorm	Statistics
POISSON	ppois when cumulatic,dpois when not	Statistics
POWER	^	Arithmetic
PROB	ecdf	Statistics
PRODUCT	prod	Arithmetic
PROPER	toupper	Text
QUARTILE	quantile	Arithmetic
QUOTIENT	%/%	Arithmetic
RAND	runif	Arithmetic
RANDBETWEEN	sample	Arithmetic
RANK	rank	Essentials
REPLACE	sub,gsub	Text
REPT	rep and paste or paste0	Text
RIGHT	substring	Text
ROUND	round	Arithmetic
ROUNDDOWN	floor	Arithmetic
ROUNDUP	ceiling	Arithmetic
ROW	row,:,seq	Essentials
ROWS	nrow	Essentials
RSQ	summary of lm object	Statistics
SEARCH	regexpr,grep	Text
SIGN	sign	Arithmetic
SKEW	skewness in the moments package	Statistics
SLOPE	in coef of lm object	Statistics
SMALL	sort	Arithmetic
SQRT	sqrt	Arithmetic
STANDARDIZE	scale	Statitics
STD, STDEV	sd	Arithmetic
STEYX	predict on an lm object	Statistics
STRING	format,sprintf,formatC	Text
SUBSTITUTE	sub,gsub,paste	Essentials
SUM, SUMIF	sum	Arithmetic
SUMPRODUCT	crossprod	Arithmetic
TDIST	pt	Statistics
TEXT	format,sprintf,formatC	Text
TINV	abs(qt(x/2,data))	Statistics
TODAY	Sys.Date	Essentials
TRANSPOSE	t	Arithmetic
TREND	fitted of an lm object	Statistics
TRIM	sub	Essentials
TRIMMEAN	mean(x,trim=tr/2)	Arithmetic
TRUNC	trunc	Essentials
TTEST	t.test	Statistics
TYPE	typeof,mode,class	Essentials
UPPER	toupper	Text
VALUE	as.numeric	Arithmetic
VAR	var	Essentials
VLOOKUP	match,merge	Essentials
WEEKDAY	weekdays	Essentials
WEIBULL	pweibull when cumulative,dweibull when not	Statistics
ZTEST	pnorm	Statistics